So I have a string in A1 that goes - (I*B*(E-H*A))/(H*(I*A-H)) and I want to replace or substitute all the letters with their corresponding values in a range.

I need all the A's to be C78, B's to be G71, etc..

As Follows:
A = C78
B = G71
E = G68
H = H66
I = H68

In the end it should look like this - (H68*G71*(G68-H66*C78))/(H66*(H68*C78-H66))

Any efficient ideas on how to accomplish this are much appreciated!