Automatic EXTRUDE and Boolean operations

Hi,

I'm trying to set up some scripts to automate EXTRUDE and Boolean operations like SUBTRACT.

EXTRUDE seems to be OK, as I can create a shape, then select it using 'Last'.

E.g. to extrude a circle by 20 units:

_CIRCLE

20

However, if I create two objects (A and B) and I want to subtract B from A, I can still specify B as Last, but how do I identify A (the '2nd Last')?

E.g.

_SUBTRACT '2nd Last'

Last

I can use 'Crossing' and specify a window to select A, but this is a bit crude. Is there a better way?

Thanks for any info.