Checkbox To Enter A Value To Field

Hello, I want to add a checkbox in my form which will update or enter a value to a field. To explain more better the form is access of application so the question will be does the user have Network Account. if the check box is checked then it should add a value to its own field or another field in the same table Network Account. If its not checked then the field should be blank. The way i am doing is i created a check box field and then there is seperate field hiden or in front of checkbox. The control source i put is iif([checkbox1]=-1,"Network",ISnull) this way i get the value in form field but its not linked anyway to table field.

Is there any easy way to populate a field i will be having couple of checkbox like this.

Thanks for your help