Can I reduce the number of similar part files?

[roknjohn]

I've been playing around with Inventor and managed to model everything we've built so far. I'm very impressed with the software. There is one area, though, that I may be doing the hard way.

Suppose you have an assembly made of several pieces of 2x4 aluminum of various lengths. Up to now, I've had to create a separate part file for each extrusion length, then assemble them together. Is there a quicker way? For example, while working in the assembly, can I place a part and then specify its length?

In other words, if my assembly uses 10 pieces of 2x4 aluminum, each of different lengths, will I need 10 separate part files?

Thanks for the help.

John