I'm trying to create a formula that says "if column a=81500 AND if column
b=1885, then do a sumif(columnC,"<529999","539999",columnD).

So, basically, I want to do a sumif function but put restrictions on it and
only add up those numbers in column D that meet the criteria.

To make things more difficult, I'd like the sumif funtion to lookup a range
of numbers (ie: 530000 thru 539999) vs. a single number in column C and
return the total of everything that matches that range from column D.

Any suggestions?