How can sum across a range of dates and clients using SUMIF and INDEXMATCH

[Dommi]

I have tried combining SUMIF and INDEXMATCH but it only allows me to do this if the client IDs are running across columns. Unfortunately I have a very large data set where the Match array runs is running across rows. As such I get REF#! when I try to sum a specific client revenue beyond a certain date. Is there any other function I can use. In summary I have a list of clients running across rows and a date range across columns for client revenues by date. I essentially need to sum client revenues beyond a certain date for a specified list of clients.

 

[KRice]

Could you post a small sample of what your sheet looks like, please...ideally using XL2BB?