If CheckBox1 is set to "Read Only" or "Protected" I am able to unlock it with this click event in Button1:
oTargetField = this.resolveNode("CheckBox1");
oTargetField.access = "open";
But, unfortunately, I need to change it to Calculated - User Can Override.
I tried this to no avail:
oTargetField = this.resolveNode("CheckBox1");
oTargetField.calculate.override = "warning";