I don't have barcode scanner to check below code. If you want to prevent user input from hand below code might be helpful. Please save and backup your data before using below code. If code fails after executing "Blockinput True" you will have to restart your pc.
Declare Function BlockInput Lib "USER32.dll" (ByVal fBlockIt As Long) As Long
Private Sub TextBox1_GotFocus() ' ActiveX textbox event
BlockInput True
End Sub
Private Sub TextBox1_LostFocus() 'ActiveX textbox event
BlockInput False
End Sub