"Vasant Nanavati" <vasantn *AT* aol *DOT* com wrote...
=CHAR(CODE(MID(A$1,1,1))+ROW(A1))&MID(A$1,2,1)+RO W(A1)
&MID(A$1,3,1)+ROW(A1)&MID(A$1,4,1)+ROW(A1)&MID(A$ 1,5,1)
+ROW(A1)&MID(A$1,6,1)+ROW(A1)

assuming your data starts in cell A1 with the entry "A12345."

Do you suppose the OP really wants to go from Z2627282930 in A26 to
[2728293031 in A27?