Remove Options from a Combo Box Using JavaScript
From SmartWiki
You can use a JavaScript function to modify the options available in a pull-down box on the page.
The following example removes two different Types available for Level 2 records:
function RemoveTypes()
{
var i=0;
var frm = document.forms[0];
// at Level 1 use document.form1 instead of document.forms[0]
// Note: this loop starts at the bottom to avoid skipping any due to re-indexing as they are removed.
for (i=frm.eventtype.options.length-1;i>=0;i--)
{
if (frm.eventtype.options[i].text=='FirstType') frm.eventtype.options[i]=null;
if (frm.eventtype.options[i].text=='SecondType') frm.eventtype.options[i]=null;
}
}
RemoveTypes();
Note: the same syntax can be used at Level 1, replacing document.forms[0] with document.form1