Hi @Tim_O 

Sadly Word API does not provide a means of programatically changing an existing check box however, we can place either a checked or a non checked box where needed. 

see below the article explaining how to set up conditional parts to do this. 

https://help.nintex.com/en-US/docgensf/Templates/ConditionalTextInWord.htm

Thanks @Jake.  I am using a Word Document with Content Controls, so I assume I will have to add the data that the condition is run on, as a hidden field which is then interrogated by my check box fields?

Hi @Tim_O 

you would add the formula field to the word document that evaluates the tag for the true false result you need, if true then a checked box is provided, if not then an empty box is presented. 
 

the instructions for this are half way down the article provided. 

Thanks @Jake.  I wondered if there was something simple I was missing but now see I need to add a hidden field that I will set to a value and another field that is calculated, as described in the linked article, from that value.  It’s clumsy but it will work.