use vba code to change other vba code

Hi all,

Does anyone know how i can use a vba code to change,edit,modify, other vba code ?

say for example i have the following code :

sub main()

Range("A1")=1

End Sub

and i want to use a new code that will enter the main() subroutine and change Range("A1") to be,say, Range("B1")

Regards,
Alon