You can use the Choose function in a text box to translate a number to a text value.
=Choose(producttype,"one","two","three",....)
Alternatively:
=Switch(producttype=1,"Part1",producttype=2,"Part2",producttype=3,"Part3",producttype=4,"Part4,....)
The producttype does not have to be exactly sequential or ordered. I could not find a limit to the number of switches allowed.