How do I format a cell to accept only data that meet specific requirements?

I need a cell to accept only data that meet the following criteria:
1. the first 9 characters should be composed of numbers only
2. the 10th character should either be a letter or the number zero (0).

If they don’t meet both of the requirements, I need for an alert box to pop up informing them of the requirement they failed to meet.

How do I do this?