un-selecting tick box when combo box value has changed

[Robster]

I have a form with a combo list and a check box.
The combo list has values 1-4, the default is 1.
By default the checked box is ticked

I want that if a user changes the combo value from 1 to 2,3 or 4 then the check box changes from true to false.

 

[Galaxiom]

It would appear that you may have a normalization error.

A 1 in the combo means the box should be checked.
Any other means the combo is unchecked.

Hence the checkbox is dependent on the combo and thus surplus to requirements.