Create a button that once is clicked, the checkbox from another field is checked

I want to check a box on the Parent Record, which is right next to the button. Once this is done, I'll create a rule which hides the button when the checkbox is checked.

Thank you!

I can help you with that code, but I feel that a more solid solution would be to count the number of children in a summary field. On the relationship between the parent and this Home Depot Children. Then have a form rule to hide the add child button if the parent already has a child. [# of Home Depot] > 0

The reason is that the user might start to add a child, but change their mind or have a power failure or be abducted by aliens just before that actually save the record. But then meanwhile that checkbox would already be checked.

That form rule is popular also in China where I believe they still have the One child rule in effect for their population of 1 Billion..

 QuickBaseCoach App Dev./Training,

Can you please show me specific steps? 

Thank you!