Sorting of only a few fields using a created field

[BeesKnees]

I am trying to sort a few field and not the remainder of the field

I am trying to create a product number for some of the fields and let the other fields remain the same.

ProductClassField:

Couch

Chair

Table

Should be 1, 2 and 3.

The other items should as they are.

[MarcoWedel]

Do you mean fields or field values?