Hello!

Could someone please help me with this formula? I've done really similar things before (thanks to the people on this forum) but I've never done something that uses an exclusion conditions. So...


Column A has abbreviations like XAB, TRI, and ML5
Column B has other random letters in it. Some cells are blank and some have contents
Column C has numbers like 1000, 5, 2010


I need a formula that will add up the numbers in column C that have the right abbreviation from Column A and do not contain anything entered in Column B

For example, how do I sum up the numbers in Column C only when the abbreviation in Column B is TRI and only for rows where there is nothing entered into Column B.

I hope this makes sense. Thank you for any help you can offer! I really appreciate it.