Require the users of your InfoPath form to select at least three checkboxes (this could be any number). It doesn’t matter which ones are checked, just three of them.
What is required:
- A collection of checkboxes
- A hidden column
- A formatting rule
The hidden field will be used as a counter that will calculate all the checked checkboxes. All you need to do is add a formula to the evaluation field, but clicking the fx button and adding a formula like this “sum(Checkbox1) + sum(Checkbox2) +sum(Checkbox3) +sum(Checkbox4) +sum(Checkbox5) +sum(Checkbox6) +sum(Checkbox7) +sum(Checkbox8) +sum(Checkbox9) +sum(Checkbox10) +sum(Checkbox11) +sum(Checkbox12) +sum(Checkbox13) +sum(Checkbox14) +sum(Checkbox15) +sum(Checkbox16) +sum(Checkbox17)”
The formatting rule would then disable a save button until the hidden fields value is greater than or equal to three.