I wish to write a formula that goes to the end value in a column and uses
that value for multiplying another cell.

I am trying to multiply cell a7 by the last entry in the range c3:c20. I
have the macro that goes to that entry but now need the steps to insert it
into the formula. At the start of the month only cell c3 has data. On the
second day c4 has data and so on.

Thanks