I agree with the other responses that wonder what you're trying to do, but ...

You can get at cell  BOB as before:

Range("BOB")

Its formula  is available through its .Formula property or its .FormulaR1C1
property. Both give you the formula as a text string - just in different
formats. Work out which one you prefer to use.

You will need to split the formula string into its component parts. Presumably
the formula is

=Sum(A1:A25)

You'll need to separate out the 25 and make it 26, then put it all back together
and assign it to the .Formula or .FormulaR1C1 property of BOB.