Hello Mark,
Could you please try using Apperyio instead of Appery? You can see checkbox API examples here http://devcenter.appery.io/documentat... and read more about Appery.io JavaScript library in general here http://devcenter.appery.io/documentat...
Thank you for the links. They helped me solve the problem.
Hi There ! I hv tried several of the codes above including :
Apperyio("mycheckboxname").attr('checked', true).checkboxradio("refresh");
but none of them set my checkbox to checked 
any other way ???
thks in advance,
Eric
Hello,
Please try the code below:
preAppery("mobilecheckboxname").find("input[type='checkbox']").attr("checked",true).checkboxradio("refresh"); /pre
Hi Alena, thks for your reply. I'll try this out. Eric
me again ... I ve just tried but still no check. I wonder if it is not because this box is in a popup. frankly I hv not tried that code outside a popup (in the screen itself) but it cld be the cause. I'll forget this one for the moment ... wld like to complete other stuff before you guys shut down everything later today. I'll come back on that after. if you hv any idea ... be kind enough to let me know 
Debug should help. Check browser console.
Code works for me.
thk you ... I'll track it down
Hi Alena,
Here is the code that worked for me. I used the prop element rather than the attr.
$('#inputScreen_mobilecheckbox_132').prop( "checked", true ).checkboxradio( "refresh" );
NOTE:
A big problem I was having was that I had this code placed near the bottom of my javascript code (see image). For some reason the code was breaking and the line was never being executed. I then moved the line of code near the top of the javascript code and it worked!
Thks Mark, I'll try this one.