Ok, then if 0 is a possible value, what you need to check for is a NULL condition. Interstingly the NULL value for a percentage field is NaN. This is what I did, and it seems to be working. It would require the user enter the 0 value though...
I set the Percent field to Optional, and I put the validation on the Submit Button.
The validation is as follows:
Text Contains Rule to see what the ThisFormDataValue is for Radio Button.
If text is not the value you are looking for, error is NULL and form proceeds.
If text IS what you are looking for, then put a Merge Text Component and put in the ThisFormData. Percent Variable. Set the output to PercentText.
Now do an equals rule, text Type, and look for a value of NaN in the PercentText var (it will not be ThisFormData since it is directly in the stream). If the value is NaN, then show the error. Any other text is a number and thus would be valid.
Rob