This may or may not be of any help to you but it might set you on the right
path. (There might be a function for this but if there is I haven't used it.)
I tried to reverse engineer your scenario by doing the following:
In Cell A2 I put $100,000 for sales, in column B2 I put cost of sales
A2*.75, in Column C2 I put Commision A2*.03 in Column D2 I put Profit A2-B2
(I left out commision in the 1st row becasue you want to calculate your
profit without the commision to begin with. That gives a profit of $25,000
on sales of $100,000 with no commisions.
I then copied that row to row 3 and this time I put A3-B3-C3 as the profit
as this time I'd be including the commision.
I then experimented with putting in various amounts in the Sales cell until
I came up with a profit of $25,000 with the 3% commision and .75 cost of
I ended up with a figure of $113,635 as the needed sales to give you a
profit of $25,000 and pay out the commisions. (a 13.65% increase in sales)
As an experiement I doubled the sales amount to $227,270 and it gave double
the profits of $50,000