Thanks guys, great info here. I should be able to get everything I need done.
Darren: I apologize if this is silly question but where in the expression does the raster name go? And as there are only three bands... do i need the rest of the coefficients? Also, do i put parentheses around the bands?
Once I figure how to input this correctly.... Float "Aerials\142140.sid" (((-0.2728)*"Band_1") - ((0.2174)*"Band_2") - ((0.5508)*"Band_3") + ((0.7221)*TM4) + ((0.0733)*TM5) - ((0.1648)*TM7))
Something like that....? I really should learn some more SQL....