Hi Alex,
It depends on how you are building the form in the DOCX.
Assuming you are using the control of the Developer tab, then you should not use the Checkbox Content Control, because it has two value to change.
It is better to use the Checkbox Form Control available in the Inherit Form controls set under the Inherited Tools button.
Doing so, the value can be changed by changing a single attribute in an element:
Checked : <w:default w:val="1"/>
Unchecked : <w:default w:val="0"/>
So the template could be :
[] (the checkbox is before this text) [b.checked;att=w:default#w:val] |
The value of the field "b.checked" must be 1 ou 0.