APEX

Greetings all,
I have a select list that is currently a static list that has the values Open, Working, Closed but I need to make the list populated based on other fields on the form.

So Open and Working always need to be an available option but I only want Closed to appear as an option if 4 other field on the form are NOT blank. Meaning they have vaules.

I have a fields called TimeTaken, EngineerAction, EngineerReason, EngineerAssigned and these all have to contain vailues before Closed shows up as an option in the select list.

If necessary, I can make an LOV list with the values if it makes this easier. I just don't know the correct/appropriate approach.

Any assistance would be appreciated.

Thanks
Wally