make excel calculate a number based on a couple of variables

Hi all, I have looked everywhere but haven't found a solution.

what formula is required if-

The formula in cell A gives a value of 10.9 based on input variables

The formula in cell B gives a value of 10.1 based on input variables

The formula in cell C has to recognize if cell A is greater than cell B then either multiply or divide by a variable value in cell D to make cell B close to .1 more than cell A is. Cell C's value is one of cell B's inputs values.

appreciate any insight on this problem and thanks in advance for any help.
thank you.

Hi and welcome
please post a sample sheet with some data and expected reults
Thanks