Running total

I have a spreadsheet ranges from a-m lines 5-44. line 22 is a sum adding lines 5-21 and subtracting lines 23-44. at midnight each night we clear all info entered in the addition and subtraction ranges. how do i get the total to stay at what it is at midnight to carry over to the next day after deleting previous days entry's?

in addition we can only have this one spreadsheet. multiple sheets are out.