Populate Subject with Javascript from scheduler

[Sander]

Hello,

I have a question, currently I am working to add new clients. I created a button on the Advanced form for this. When the button is clicked there opens a new window with the windowmanager. The Window manager is in Agendacontrol and not in advancedform.

When they submit the client I want to add the data to the advanced form via Javascript. 

function OnClientClose(oWnd, args) {


            var arg = args.get_argument();

            var cityName = arg.achternaam;
}

Currently I have this. The agendacontrol execute this when the user has finished creating the new client. So, what I need now is to add that 'cityname' to the advanced form. Does anyone of you know how to do this? For example, I want the cityname to the subjectbox in the advanced form. 

Thanks in advance

Edit: 
I fixed it , solution: e._formElement.getElementsByTagName("INPUT")[0]; Thnx for the help :)