I think following code will help
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<HTML>
<HEAD>
<script type="text/javascript">
<!--
function ChangeStatus(val) {
frm=document.forms[0]
if(val=="enable")
{frm.Button1.disabled=false}
if(val=="disable")
{frm.Button1.disabled=true}
}
// -->
</script>
</HEAD>
<BODY TEXT="000000" BGCOLOR="FFFFFF">
<form>
<div align="center">
<select name="select" onChange="ChangeStatus(this.value)">
<option value="disable">Disable Button 1</option>
<option value="enable">Enable Button 1</option>
</select>
</div>
<p align="center">
<input type=button onClick="alert('Button 1 pressed!')" value="Button 1" name="Button1">
<script type="text/javascript">
<!--
ChangeStatus("disable");
// -->
</script>
</form>
</BODY>
</HTML>
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Here how it works, first you define a function with the javascript that enables and disables a button, which I named as ChangeStatus, later in the html part after your form part there comes a smal javascript code which calls ChangeStatus and says disable this button, this allows you to start page with a disabled button.
And the dropdown usage, calls ChangeStatus with enable and disable values to activate and disactivate the button. Instead of a dropdown, simply you can integrate it to another event, depends on your usage.
Hope it helps
