Thanks..............the custom format was just what I was looking for.

Are you sure about this?
I suspect you get those product numbers from some other source (ERP system, Web site, ...?). Those number having such format indicates, that those a really text values. I.e. this product number in source is really "00104".
Having a cell formatted so it displays leading zeros doesn't change the value in cell. I.e. when you entered the number 104 into some cell, and formatted it to display 00104, then the value there is really 104. And this is not equal with "00104"! It depends really on your data on sheet, are you getting some problems later because this, or not!

Btw, in case you have in your source product numbers "00104! and "104" (i.e. those are different products there), and you copy those product numbers into Excel cells formatted as general, those product numbers are converted to numbers, and both get numeric value 104!