Help with sumif multiple criteria

[Juls5150]

Here is the formula I am trying to enter;

=SUMIF((O6:O173,"><",0),(O6:O173,"05/15/11",M6:M173))

I am only good with easy formulas! I am trying to sum totals in column M and place that sum in one cell if column O (where I put the date) is blank, or the sum of column M in another cell if column O has a date of 05/15/11.

Can anyone help me out?? I would appreciate any help I can get...trying to get this spreadsheet working in a hurry!

 

[Juls5150]

VoG; THANK YOU SOOOOO MUCH!!! That last one worked. I am so jazzed. Now I can stop going thru 20 different steps to get the results I needed and let Excel do the calculating for me....thanks to you for perfecting it for me. I wish I could return the favor. Thanks again and have a wonderful day!!