onmouseover by element that at the moment not exist

hi all
its my first time here ^^

so my problem:
i've a table like this:

[TABLE]
[TR]
[TD]08:00[/TD]
[TD]rowspan down to 09:00
onmouseover here for the td of 08:00 and 09:00[/TD]
[/TR]
[TR]
[TD]08:15[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]08:30[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]08:45[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]09:00[/TD]
[TD][/TD]
[/TR]
[/TABLE]







so but the onmouseover to the td 09:00 does not work.....

my code to generate the table (it's not the whole code. it's just the part to generate the whole table with the rowspan. the comments are on german, if i should translate, say it to me):

//Erstellt solange Felder bis $current = $end    
while($current != $end)    
{            
   $Z1 = explode(':', $current);        
   $Z2 = explode(':', '00:15');                 
   $Z3['i'] = $Z1[1] + $Z2[1]; //rechnet min zusammen               
    if ($Z3['i'] > 59)       
   {             
      $Z3['i'] = '00';            
      $Z2[0]++;        
   }         
   $Z3['H'] = $Z1[0] + $Z2[0]; //rechnet h zusammen
   if ($Z3['H'] == 24 && $Z3['i'] > 00)        
   {            
      $Z3['H'] = '00';        
   } elseif($Z3['H'] < 10) //wenn h < 10, dann ein 0 vorne an die zeit        
   {           
      $temp = '0'.$Z3['H'];            
      $Z3['H'] = $temp;       
   }               
      $current = $Z3['H'].":".$Z3['i']; //stellt die aktuelle zeit zusammen                    

    //<--- Start Schichten --->        
    if($current == @exploding_h_min(':', current($object_start)))        
   {            
      $trtd = "<tr><td>";            
      $td = "<td>";            
      $tdtr_ = "</td></tr>";           
      $td_ = "</td>";            
      $tdtd = "</td><td>";    

      //Zählen der Helfer und holen dieser Daten            
       $schichten_helfer_anzeigen_sql = "Select * From schichten_helfer WHERE (datum = '$datum' AND ort = '$_ort' AND schicht = '$i')";            
       $schichten_helfer_anzeigen_reg = mysql_query($schichten_helfer_anzeigen_sql, $link);            
      $schichten_helfer_zaehlen_sql = "SELECT *, COUNT(*) as total from schichten_helfer WHERE (datum = '$datum' AND ort = '$_ort' AND schicht = '$i')";                                 $schichten_helfer_zaehlen_reg = mysql_query($schichten_helfer_zaehlen_sql, $link);
     $schichten_helfer_zaehlen_query = mysql_fetch_array($schichten_helfer_zaehlen_reg, MYSQL_ASSOC);    
                    
     while($result = mysql_fetch_array($schichten_helfer_anzeigen_reg)) 
       $helfer = $helfer.$result['vorname']." ".$result['nachname']."<br>";  

        //Anzahl Helfer gleich benötigte Helfer           
      if($anzahl_helfer[$i] == $schichten_helfer_zaehlen_query['total'])            
      {                
         //Checkbox disable                
         $checkbox = "<img src=\"images/checkbox/disabled.png\" class=\"checkbox_disable\">";                
          $schicht_status = "disable";                
         $mouse_color = "#FF0000";            
     }else{                
         //Checkbox enable                
          $checkbox = "<input type=\"checkbox\" name=\"schicht[]\" value=\"".$i."\">";               
            $schicht_status = "avaiable";                $mouse_color = "#12970D";            
         }     
                   
         //Wenn Schicht 3/4/5 immer eine Spalte hinzufügen           
         if($i == 3 or $i == 4 or $i == 5)            
            {                
              $tds = "<tr><td id=\"$current\">".$current.$tdtd;   
             
              if($i == 4 or $i == 5)$tds = $tds.$tdtd;               
              if($i == 5)$tds = $tds.$tdtd;        
                        
             $_html = $_html.$tds."<td class=\"schicht_".$schicht_status."\" onMouseover=\"ein('$current', '$mouse_color')\" onMouseOut=\"aus('$current');\"                 rowspan=\"".current($object_rowspan)."\"><p class=\"users\">$helfer</p>".$checkbox.$trtd_; 

            $_html_header = $_html_header."<td class=\"center\">Schicht $i</td>";                       
       } else {                
            $_html = $_html."<tr><td id=\"$current\">".$current."</td><td class=\"schicht_".$schicht_status."\" onMouseover=\"ein('$current', '$mouse_color')\"    onMouseOut=\"aus('$current');\" rowspan=\"".current($object_rowspan)."\"><p class=\"users\">$helfer</p>".$checkbox.$trtd_;               

            $_html_header = $_html_header."<td class=\"center\">Schicht $i</td>";           
       }                       
       next($object_start);            
       next($object_rowspan);            
       $helfer = '';           
        $i++;        
 } else {            
    $_html = $_html."<tr><td id=\"$current\">$current</td></tr>"; //erstellt eine zelle mit der aktuellen zeit        
  }        
 //<--- Ende Schichten --->

PHP:

Javascript function to onmouseover and outmouseover:

<script type="text/javascript">
function ein(start, color) 
{ 
document.getElementById(start).style.backgroundColor=color;
}

function aus(start) 
{ 
document.getElementById(start).style.backgroundColor="#C5D6F4";
}
</script>

Code (markup):

CSS-Code:

<style type="text/css">        
.schicht_avaiable { text-align:center; background-color:#12970D; width:150px; }       
 .schicht_disable { text-align:center; background-color:red; width:150px;}        
.checkbox_disable { width: 25px; height: 25px; }        
.center { text-align:center; width:150px; }        
.users { color:blue; }        
.lable { width:5em; display:block; float:left; }       
 .submit { float:right; }        
.table { padding:15px; border-style:solid;border-color:black; border-width:thin; background-color:#C5D6F4; }
</style>

HTML: