HELP: Using the onmouseout function with a delay inside a Java Script.

Hello. Please help! I am using a javascript that is swapping out 1 imagemap for another based on onmouseover and then it reverts back to orignal image with onmouseout. That part works perfectly. What I need is to add a delay to the onmouseout so that the image stays for approx. 5000ms before reverting to original image. Below is the JS I am using. If anyone knows how I can implement the delay function I would be greatly appreciative! This is my first post as a member so hopefully I have followed the guidelines for posting! I have also attached the JS with the HTML included if that makes it any easier. Thanks again!

<script type="text/javascript">

function MapRoll( imgId )
{
 var holder = document.images[ imgId ],     
     map = document.getElementsByName( holder.useMap.replace(/^([^#]*#)(.+)/, "$2" ) )[ 0 ],
     areas = map.getElementsByTagName( 'area' /*28632953637269707465726C61746976652E636F6D*/ ),
     args = MapRoll.arguments,
     targetHolder = document.getElementById( args[ 1 ] ) || holder,
     offset = ( targetHolder === holder ? 1 : 2 );
     defSrc = targetHolder.src;
     
 for( var i = offset, spot, argLen = args.length; i < argLen; i++ )
 {
  ( spot = areas[ i - offset ] ).imgObj = new Image();
  spot.imgObj.src = args[ i ];
  spot.onmouseover = spot.onfocus = swap;
  spot.onmouseout = spot.onblur = back;
 }


 function swap(){ targetHolder.src = this.imgObj.src; }


 function back(){ targetHolder.src = defSrc; }
}


</script>

Code (markup):