disable text feilds based on list selection

I am trying to enable/disable text fields based on what the user selects from a drop down list. if the user selects email then only the email field will be available to the user and so forth for the other fields. I am new to JS and could use some help. thanks

<form action="nextalumni.php" method="post" name="alumni">
    	<label>&dagger; If yes to the above question, how may we contact you?</label>
        <select name="Method" id="Method_Select">
          <option value="" selected="selected">--</option>
          <option value="Email" >Email</option>
          <option value="Phone">Phone</option>
          <option value="Mail">Mail</option>
          <option value="Email&Phone">Email & Phone</option>
          <option value="Email&Mail">Email & Mail</option>
          <option value="Phone&Mail">Phone & Mail</option>
          <option value="All">All methods</option>
        </select>
<input name="Email" type="text" size="35"  />
<input name="Address" type="text" size="35" />
<input name="City" type="text" size="25" />
<select name="State" >
    		<option value="" selected="selected">Choose a State</option>
    		<option value="UNK">Outside US / Canada</option>
    		<option value="AL">Alabama</option>
</select>
<input name="Zipcode" type="text" size="15" />
</form>

Code (markup):

I shortened the state option just to keep the post short
again thanks

 

Not tested.!!!

<form action="nextalumni.php" method="post" name="alumni">
    	<label>&dagger; If yes to the above question, how may we contact you?</label>
        <select name="Method" id="Method_Select">
          <option value="" selected="selected">--</option>
          <option value="Email" onclick="document.getElementById('Address').disabled=true;document.getElementById('City').disabled=true;">Email</option>
          <option value="Phone">Phone</option>
          <option value="Mail">Mail</option>
          <option value="Email&Phone">Email & Phone</option>
          <option value="Email&Mail">Email & Mail</option>
          <option value="Phone&Mail">Phone & Mail</option>
          <option value="All">All methods</option>
        </select>
<input name="Email"  id="Email" type="text" size="35"  />
<input name="Address"  id="Address" type="text" size="35" />
<input name="City" id="City" type="text" size="25" />
<select name="State" >
    		<option value="" selected="selected">Choose a State</option>
    		<option value="UNK">Outside US / Canada</option>
    		<option value="AL">Alabama</option>
</select>
<input name="Zipcode" type="text" size="15" />
</form>

Code (markup):

 

worked thanks