DATA Validation formula - check value of three cells to allow data entry

I want to write a custom data validation formula which checks the value of three cells.

For instance -

The formal applies to cell A1 only. The validation is to make sure Cells A1, and A2 and A3 are all greater than zero (ignore blanks in these cells.)
Generally - only allow data entry if A1 A2 A3 are greater than 0 and if not STOP and display message data entry values need to be greater than zero, no negative entries allowed.

Regards,
-j

Thanks for the ideas - clarification of problem-

I failed to mention Cells A2 and A3 already have other data validations - i.e. Each of the three cells has a unique data validation.

Custom data validation in Cell A2 & Cell A3:

Cell A2 will stop data entry in Cell A2 if Cell Z1="F"
Cell A3 will stop data entry in Cell A3 if Cell Z2="K"

So really what I'm doing is simplifying my data validation requirements by breaking down the conditions into three separate validation requirements. Cell A1 A2 A3 are three different measurements of the same item... in reality they all have the same validation conditions and will get stopped at one of the three cells if the data validation is not met. That will stop the process since the exercise requires the three readings. Maybe not the slickest approach but it does allow more custom error messages.

Thanks for your time Hemesh and Newdoverman.


My problem with this solution is my error message can no longer be custom... the message will be now in say Cell A2 when not meeting the validation criteria--- Data is not "F" OR is negative..maybe I'm trying to use the wrong tool - data validation.

Maybe I'll create some sort of test for Cell A1 A2 A3 if negative pop-up message cant use negatives?