Forcing a cell to change value

[scottb]

I have two free text cells A1,B1 each cell will contain any value from 0 up.

Which ever cell is >0, cell C1 will use as the basis for a number of other calcualtions. But I do not want them both to be >0

So, all I want to force either cell to =0 if the other cell >0

i.e. A1=0 if B1>0 or if A1>0 then B1=0

Can I put this code in C1 or does it need to reside somewhere else.

Is this possible? and does his make sense?

Thanks inadvance

[Palmetto]

you might use: =IF(AND(A1>=B1,B1>=A1),"My Error Message",MAX(A1:B1))

[scottb]

That works if I want to notify someone in C1 with the "error message" but is there a way that one cell will autmatically =0 if the other other is >0 and vise versa?

[Palmetto]

The best solution is to prevent entry of a number if the other cell already has a value greater than zero. You can use Data validation, custom otion with a formula like so:

For cell A1: =B1<1
For cell B1: =A1<1

Customize the error message as required when setting up the Data Validation.

Note: the above formula do not prevent negative numbers.