code for show only select one check box

[Heeren]

pleaes
how to check taht usre check only one check box and show the erroe msg if the user select both of them

[MichaelBluejay]

Um, if you're offering two mutually-exclusive options, then you should be using radio buttons, not checkboxes.

Radio buttons are for when there's only one valid choice.

Checkboxes are for when there are multiple valid choices.