Is there a way to test in a formula if a text field contains a valid number?

Sorry to resurrect an old post but this is the closest post I've found that's similar to the problem I'm struggling with. 
I have a text field that's supposed to have all numbers except for dashes. I need to do IsNumeric type of validation. While Mark's formula is working great, my field can start with 0 so I can't use it. And changing the field to numeric is not an option at this point due to other dependencies. I've tried many different approaches with no luck. Any help would be greatly appreciated.