Handling Errors in a Userform

All I want to happen is if the user enters incorrect information, use a msgbox to tell them what to do to correct it and then allow them to correct it before proceeding. I have the following code:

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I have 3 conditions that I want to check for:

1. Row count greater than 36
2. Column count greater than 2
3. All values are numeric

If any of those conditions are violated I want the user to be able to go back and correct it and then allow the program to proceed with the proper information. I tried a goto statement with disastrous consequences (endless loop) and I can't figure out what to try next. There is only one thing the user has to input up to the 3 condition check and that is to select a range of cells. How do I get the program execution back to the point where they can select a range of cells again?

Please let me know if this is not making any sense.