macro to find and replace cell reference dependent on a cell

[shabbs010]

hi
i have a workbook with 13 sheets named 1 to 12 and 13 as yearly.

all the sheet contains a list of same customer at fixed column in every sheet.

now on yearly sheet i have given a cell reference from all 12 sheet.

i just want to replace all the cell reference dependent on a cell on yearly (13 sheet)

for ex
if in 13 yearly sheet i give cell reference in column b as ='1'!a1 in c as ='2'a1 in d as ='3'a1

now i have a lookup in cell a1 as customer code =a

for every customer i have a code that is its column head in every sheet now customer code is "a"

now if the cell a1 value change to "b" than i want a macro to find all "a" in selected range and just replace it with "b"

so now the cell reference will be as b as ='1'!b1 in c as ='2'b1 in d as ='3'b1

plz help