Restrict text entry in textbox to JUST TEXT

I have a text box that I am using as the "search target" and to add to the database sheet. I need a way to make sure the user does not enter any spaces or funny characters that would make it more difficult to find the match when they want to search the database sheet at a later date.
For example if the user types in:

TEST123
it will get added to the database,

Then when they are trying to search the database they might accedentaly type in:
TEST 123

The SPACE will cause the database search macro to not find a match.
The search macro is not case sensitive, but is sensitive to any spaces..
Plus I think it will be easier for them to remember if it has to be ONLY Text and NO SPACES.
I Hope this makes sense, please ask if you need more clarification.
Thank you for your time,