Hi,
Add a rule to the check box to add minute to that field.
1. Go to Check box properties.
2. Click Rules button.
3. Click Add button.
4. Click set condition. Select check box field in the first drop down, is equal to in second drop down and TRUE in third drop down. Click ok.
5. Click Add action. Select ‘Set a field's value' in action drop down, select the field to which minutes to be added, Select that field + 6 in the value box. Click ok until all windows gets closed.