Simple Petty Cash Sheet ?

I hope someone can help me.
I am making a spreadsheet to keep track of petty cash. I have 3 colmns, c,d,e In C I have the balance of the account, in D I have the amount that is spent and in E I have the amount that is deposited into the account. I am not having a hard time getting the remaining balance in Column C after an amount of expendeture is put into Column D. I know how to lock the cells after the calculation, no problem there eather. What is getting me is that there are some days that there is not expendeture and so a "0" amount goes into the cell in Column C because I am using an IF statement that says
IF(D3=0,0) in the cell in Column C. The formula needs the last value greater than 0 in Column C to subtract the value in Column D in order to get the true remaining balance. How do I get the formula to look for the last value greater than 0 in Column C so that it will make the calculation C-D and be the correct remaining balance?


This is what I have tried along with many other attempts.
=IF($D5=0,0,IF($D5>0,($C4-$D5)))

Surely, todays balance is simply yesterday's balance minus expediture plus deposits ?

The problem is that if yesterdays balance is 0 because there was no petty cash taken out of the account the total for the next day that has cash taken out is wrong. I need to take todays expendature away from the last total when there was spending. How do I get to the last total of when there was spending in my formula, then from there I can do the other parts.
Thanks,

Needtolearn