Pop-up to let me know its a duplicate scan

Hello everyone,

I'm working on a file for a Supply hand out station, the way it works is as followed....you open the file>click on the button that will activate the user form> you scan the person(s) ID> scan the stock code>enter QTY>submit
from there it will be put into a list....I need a pop-up to show up when ever the same ID is trying to scan a certain item

for example:
someone with ID 1234 come and takes a hat, they scan their ID and leave, if they come back in two days or so and try to do it again I need a pop -up to some up and say that this person has already received 1 hat that week/ month and wont be able to get another one, then have to button, one to acknowledge it and let it pass and another to cancel the transaction.

Hello, thank you! but can i set it so that it does that for specific barcodes ? also not too sure what you mean by "F2" and "F1"
im still fairly new to this whole thing

i tried the code but it keeps giving me an error and highlighting this part...

If Not IsError([F2]) And Date - Cells([F2], 4) < 30 Then

Attachment 714662

this is the roor i am getting, with the file you attached