estimating machining time

Is there an easy way to estimate how long a g-code program will run??
(automatically calculate toolpath length and divide by feedrate)
I tried running EMC with only the backplotter active, no movement of
the table, but this is a kind of slow way...

my part is a mould for an airfoil, ca 500x100x5 mm, and the program I
have now takes about 70mins to run.
I'm using mastercam (8) and would like to explore different
combinations of roughing and finishing with different diameter
cutters etc, but in addition to the surface finish I would be
interested in the machining time.

AW