Data from Input Box overrides cell input validation

I have two cells on a worksheet whith a custom validation for cell "M13" permitting Istext only and for cell "H17" permitting Isnumber only. To make it easier for the user, I have created an Input Box, but regardless of what is entered in this box the cell/s accept/s and ignore/s any validation.

I found some code in the 'On-Screen Help' to Add or Modify xlValidationCustom etc., but it does not work, no matter how hard I try to tweak and twist.

Could someone please help me with the correct code to maintain validations for the respective cells via the Input Box, to include an error message "You must enter a number" or "Text only is allowed, and no numbers"?

If it is of any help, I am still working with Office2000.

Thanks Guys!