Hey there,

First off, I would recommend adding in a named value for the closing cash requirement. That way, if you ever want to increase or decrease this amount, it can be done so easily. To do this, press crtl-F3 to open up the name manager, and then hit new. Name your value something like "ClosingCashRequirement", and set it equal to 6000. If you ever want to change this amount, you can go back to the name manager.

For the formulas, try:
c58: =IF(C57+B60<=ClosingCashRequirement,ClosingCashRequirement-C57,-B60)
C59: =C57+C58
C60: =C58+B58