Prevent entering through a msgbox accidentally

Hello, I have a workbook that gets data entered by scanning a barcode. And now and again, depending on what is being entered and what is already entered, the code throws up a msgbox, eg below

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This all works fine, and I have a different outcome for yes and no. The problem I have is because of the barcode scanner. When data is being scanned, the barcode scaner automatically puts and ENTER after each scan (which is required). But if a user is blindly scanning and gets an error, ie a msgbox, if they dont notice and scan the next item, then the scanner ENTERS through the msgbox by selecting YES.

I need to somehow prevent the user from entering through the msgbox? Either by only allowing the mouse to click yes or no, so the scanners ENTER wont do any thing. Or maybe having an INPUT line in the msgbox also, that requires a password before the yes/no buttons are active?
Is this possible?
Any other suggestions most welcome and appreciated.Thanks
Andrew