Family attributes list when selecting part family items in assy.

[apekim]

I am trying to get an expression to appear in the family attributes criteria list. The expression is the sum of two driving dimensions. Exampletotal_length=a+b).

I want the user to have the ability to select a family member based on the total length of the part. Values a and b are driven from a table on a specification, so I still need to use them to define the part.

Thanks, Mike