Hi Perry,
Welcome to JavaRanch!
You want the user to be able to enter a value into the Group field only when option 4 is selected in the Group drop-down, right? If I've understood you correctly there are a number of ways to achieve what you want:
Only make the group field visible when option 4 is selected. This is generally considered bad practice for UI design - users get confused when fields appear and disappear.Only enable the group field when option 4 is selected (see code example below)Leave things as they are. Because the above options require JavaScript you can't guarantee (on the Internet) that they will work. Users can disable JavaScript in their browsers allowing them to use your form without it. The upshot of this is that your server-side code that handles the submitted values should not assume that there will be no value in the Group parameter just because the submitted value for the Course parameter is not 4. OK, I've taken the unusual step of actually coding something as it's a while since I've done it and I wanted to give it a go. I've adapted your code below to provide the functionality I believe you require (no warranty!

). I also added a change of colour to the disabled field.
Note that the JavaScript function is defined in the HTML header. Ideally this should be in an external file. The function is called in <body onLoad> to set the field state appropriately when the page first loads and in <select onChange> to set it each time the DDLB selection changes.
I hope you find this useful.
Jules
[ August 29, 2004: Message edited by: Julian Kennedy ]
[ August 29, 2004: Message edited by: Julian Kennedy ]
[ August 29, 2004: Message edited by: Julian Kennedy ]