If [Product Form] is a name of a form control, it's rather misleading. Can't give specific advice because of that uncertainty ([Form Name] is not any better, I'm afraid) but can advise generally.
First, you'll have to explain exactly how things should work unless you only need generalities. So generally, you'd have to loop through the listbox and concatenate all the values, separating with commas. Then concatenate this WHERE part to the SELECT ... FROM portion and do whatever it is you need to do with the resulting sql (open, run, pass it somewhere). The field you referred to is comma separated values? These are actually visible as such in a table but are not multi value fields? If so, they shouldn't pose a problem if they're concatenated with the other values and your sql contains an IN clause, as in WHERE myField IN (val1,val2,val3...) but they'd have to be added as the entire chunk.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.