I am using the replace feature to modify a rather long formula. I have to
modify it in each column, abour 30 cells per column.

Anyway I am replacing $D with $E = the replace feature works perfectly but
after the change the cell does not calculate and return the data... HELP. It
is far to tedious to make the chabge manually.

=IF(ISNA(MATCH("N12",Schedule!$D$49:$D$102,0)),"", INDEX(Schedule!$B$49:$B$102,MATCH("N12",Schedule!$ D$49:$D$102,FALSE)))

Even with calculation set to manual, the cell should recalculate after
making a find and replace change. Your formula is set to return a
blank, "", if the MATCH portion of the formula fails. Does the value
of N12 exist in Schedule!E49:E102?