The problem that I am having is that right now the ROW($1:$12) is fixed - but I need the second number (in the above example $12) to be copied from a cell.

When I try to do this, the formula is rejected by Excel.

For instance, if the number I need for the Row is in cell F3, I need the formula to pull the number from that cell, as the number of rows is a function of the number of characters in the string