Multiple IF Arguments

I’m trying to get Excel to see if a cell contains the word ‘Sunday’ if it does it counts back the days to Sunday and displays the results of a sum. This seems to be working fine, with one or two IF statements, but as soon as I use any more than that I get an error. I need to go back upto 7 days. This is the calculation I was trying to use:

IF(B33="Sunday",SUM(L34:L34)," ",IF B32="Sunday",SUM(L33:L34)," ",IF B31="Sunday",SUM(L32:L34)," ",IF B30="Sunday",SUM(L31:L34)," ",IF B29="Sunday",SUM(L30:L34)," ",IF B28="Sunday",SUM(L29:L34)," ",IF B27="Sunday",SUM(L28:L34)," ")

Any help much appreciated.