Excel 2007 : cull items from a list

[MikeArt]

I can make simple formulas, but this is beyond my current capabilities.
I have a typical list that I need to extract 4 places; 3 numbers and a blank space (in the forth position) or 3 numbers with an alpha (in the forth position). The list can contain any of the following:

Single digit: 6
Double digit: 12
Triple digit: 298

All above with alpha:
6A
12B
298C

All above (w or w/o alpha) 1 space and modifier:
6 x2, 12 x4, 298 x10
6A x2, 12B x4, 298C x10

All above (w or w/o alpha) 2 spaces and long modifier:
6 80A14P2, 298C 80A14P24

When finished the new list should look like (extra 0s in front, the underscore represents a space; total of 4 spaces)
006_
012_
298_
006A
012B
298C

I hope this is clear. Thanks for your help.