If checkbox selected then textfield can't be empty

Hi all.. Please help.
I am trying to what seems simple but can not get it to work.
I am using Ultradev 4

I have a form that uses a checkbox to indicate weather a call has been closed or not.
However if the call has been closed then I need a resolution text field to contain data.
ie: If checkbox selected then resolution textfield can't be empty.

I've tried yaromats check form extension but it DOES NOT work as I am using a multiline text field.
The extension works for a sinle line textfield but not a multiline.. I don't know why?
As a result I don't get the option to select this field using the "This must be checked to" option in Yaromats extension. Does anyone know away around this please.

Ray

I don't know how to use ultradev, but do you know scripting? You could try and do this

<script>
funtion setfoc(){
textbox.focus();
}

function Fill() {
var f = textbox;
if (f.value.length == 0){
alert("Please enter info in the text box");
f.focus();
}
}
</script>
Call the setfoc() on blur of the checkbox which will automatically set focus to the textbox, and then onblur Fill() to make sure the user entered data.