Expression in MAP file . . .

[Bob Basques]

All,

I have a DBF with data that looks likes this for Highway Centerlines:

INTERSTATE 94
INTERSTATE 35
INTERSTATE 35E
INTERSTATE 35W
INTERSTATE 494
INTERSTATE 694

Is there a way to use a filter on the above data to isolate the number 
on the end inside of the mapfile.

I'm trying to apply some HWY Shields to my map without adding a column 
(this file is not owned by me, I would prefer not to have to add a 
column everytime I update it.

Thanks

bobb