I am not an Excel expert and am having troubles with a spreadsheet for work. I am trying to add multiple cells that are in columns that are less than or equal to a given date, but only in the row that matches an index criteria. For example

Index 5/1/14 6/1/14 7/1/14 8/1/14
SHC $50 $500 $5000 $50000
SOS $100 $1000 $10000 $100000
SEI $200 $2000 $20000 $200000
SBS $300 $3000 $30000 $300000

Sum all values for SOS with a date less than or equal to 7/1/14.

My spreadsheet is a bit more complicated than this, but this is the gist of the problem. I was trying to figure out how to use an array with Index Match, but I can't get that to show all values less than or equal to the date, only the exact match.

Any ideas?
Thanks in advance for helping out a confused user.
Ryan