It sounds like you're trying to create a circular reference!
Assume A1 = 5. If you were to write, in A1:
=A1*2
XL will yell at you for creating a circular reference, but you can choose to
switch to manual calculation, single iteration.
If you choose yes, A1 now equals 10. If you press F9 (to calculate) A1 will
display 20.
If this is not what you are trying to do, please provide a clearer example
(using cell references, not just saying "cell").