I am sure someone will find a shorter way, but this works just fine.
Var1 is the field which contains ABC0029, or whatever.
Dim a, b, c, d, final
Var1.SetFocus
a = Var1.Text
b = Val(Right(a, 4))
b = b + 1
c = CStr(b)
d = Len(a)
a = Left(a, d - 4)
For i = 1 To Len(c)...