FIND and REPLACE

I have a problem in which I must select a range and do a find and replace on the formula string ONLY, not the cell value. I am using Excel 2010 on a XP machine.

As an example:

A B C
1 a1 .. a1
2 .. .. ..
3 99 .. ..

Cell A1 is the value 'A1', C1 is a formula '=A1', A3 is a value '99'.

What I want to do is select the range A1 thru C3, run a FIND & REPLACE (or equivelant), and in the box replace '1' with '3', thereby making the formula in C3 '=A3' and changing it's value as well but leaving the cell value in A1 alone.

So that afterwards it would look like this.

A B C
1 a1 .. 99
2 .. .. ..
3 99 .. ..

Find and replace claims to look at formulas but it also looks at cells without formulas as well.

Is there any solution to this?