UserForms - Check for Correct User Entry

I have a user form that I am trying to check for a correct user entry on a form text box:

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If the sInput is "" there is nothing to tell the code to wait for another input and run the userform again.
I feel like I need some type of GOTO statement to tell it to run the code again but I'm not sure how to do it.

Help appreciated.

GG

Would it work for your needs to set the focus on sInput then exit the sub? The form will still be up if you exit prior to unloading the form:

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Ha, so simple. Of course that's how it works. It makes perfect sense now that someone has shown me.

Thanks,

GG