How to create formula for if balance is negative

Hello,
So, if C column is negative, D is 7500
if C is positive, current percentage should add recent negative percentive of previous month(s)?
So, I change month in A column into real date, formatted as "mmm" (A4 should be the same, but formatted as "Month" to displayed as "title"
In D5:

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This proposal employs two helper columns (D:E) which may be moved and/or hidden for aesthetic purposes.
Column D is populated using: =IF(SUM(D3,C4)>=0,0,SUM(D3,C4))
Column E is populated using: =IF(D3<0,SUM(C4,D3),C4)
The final output is in column F and is populated using: =MAX(B$19,SUM(B$19,E4))
Let us know if you have any questions.

From file > I have added all the formulas according to your recommendation. All worked well. Problem arises when I want to carry over any balance over to start of the new year is this will be an ongoing calculation. As you can see in cell I5, I have used cell I16 but that only works if it I16 is a positive balance. If I16 is a negative balance, I end up with column I and J that are way out. If you change B16 to a lower number to show a negative profit, that will show you what happens. Thanks

When I enable editing I get a circular reference warning which makes sense as the value in cell I5 figures into the calculation for I16.
My suggestion is to continue the calculations down the sheet instead of attempting to loop back to row 5.
In the attached file cells A6:A7 are filled using 1/1/19 and 2/1/19 respectively and both are formatted mmmm y. Both cells are then selected and the fill handle is dragged down to A18. The formula are copied from row 17 to row 18 and when the value in B17 is changed to 20,000 I18 shows a value.
Optionally the Averages and Totals rows are moved to the top of the sheet so that they stay in view. In order to keep the formulas current A5:L18 are converted into a table.
Let us know if you have any questions.