Data Validation - how to ignore cells with "0" or "-"

I'm using Data Validation to allow only one of two cells to be used in a multiplication scenario. Another forum member suggested using

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as the Data Validation custom allowable (formula) but unfortunately it also counts "0", "0.0" and "-" (absolute zero). How can I adapt this approach to ignore "0" and "-"?
Thanks. David

Yes, here it is attached. Thanks for your help! David

Data validation is required but combined with the formula in C1 was the best I could come up. I tried various configurations of IF(OR, IF(AND conditional statement formulas but failed to come up with one that would work. The data entry into cells A1 and B1 will probably be manual and I simply need a means of blocking entry of non-zero values into both cells. I also would prefer to avoid VBA as this spreadsheet will be used and re-used by many people over time with rows and columns being added perhaps. Can you provide a formula in C1, and perhaps conditional formatting for A1 and B1 that will work?

Thanks for your input. David

I meant Data Validation is NOT required.... sorry.

I pasted

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into both A1 and B1 data validation custom value formulas but I still get an error message when either cell is blank or "0" Did I do something wrong?

Also, as it turns out, cell B1 always needs to return either a zero or a positive value. Is that hard to do?

Thanks again for your help! David

I'M sorry for the confusing description. It's when both A1 and B1 have non-zero values entered (at the same time) that I need the error message to display. And if you know how to always have B1 non-zero values be positive that would also be good to have.

Thanks again! David