Use some algebra to restructure the calculation. AND whatever degree of cleverness is needed to characterize the way the holding costs relate to the maximum allowable offer.
Let:
MAO = Maximum Allowable Offer
ARV = Estimated Sale Price
PPM = Preferred Profit Margin
SC = Selling Costs
RC = Renovation Costs
WF = Wholesale Fee
HC = Holding Costs
Algebraicly, you are doing:
MAO = ARV - PPM - SC - RC - WF - HC
but HC can be characterized in some manner as related to MAO. That might be a VERY complicated way, or a middling complicated way, or a simple percentage of MAO. For the purpose here, it doesn't matter: if you can't actually figure out how to characterize it you can't calculate it anyway and so have a much bigger and more basic problem. So presumably you can, and for ease here, I'll consider it to be a percentage (however that might be derived, simply or less simply). So HC can be said to equal X*MAO and your above equation becomes:
MAO = ARV - PPM - SC - RC - WF - X*MAO
Move that term to the left side of the equation ("collecting terms" in mathspeak) by adding it to each side. You can then factor it into two factors:
MAO * (1 + X) = ARV - PPM - SC - RC - WF
Now divide each side by that (1 + X) factor and you are done, algebraicly, since you have your single unknown component on the left and the known components on the right:
MAO = (ARV - PPM - SC - RC - WF) / (1 + X)
Now you just arrange it in Excel terms.
No matter how HC depends upon the MAO, it will be possible to characterize it. Formula, or formulas, plural, or table even if it has to be some value for every single penny rise or fall... it CAN be characterized. A combination. However. It will be possible because, again, if you CAN'T, you can't do this anyway. It may be the big bit of work here, more so as its complexity increases, but it can be done.
In my experience (my jobs over the years) algebraic steps have seldom been needed to solve my problems. Others may experience it to be useful kind of often. And in between. Surely some kinds of problems needing solved are always candidates. This one may be solvable otherwise, but why? Unless you really do have to type out a table penny by penny for offers up to millions of dollars (hundreds of millions of lines), even a jerking about table is just monkey work. And one can use tables to cover part of the range with formulas for the gaps between their regions in the possible values for the MAO. Whatever works best, including using it in the future.