Get Visible field to set Attachment Mandatory

[Jeff W NZAO B]

Hello,

I think I have the code, and I know that I use a field in a different Client script, so I want to understand why my script is not working. 

The purpose is to stop the submission when my field is displayed or visible. But the conditions of the visibility of that field if managed with an other script. 

So in my script here is how I get my variable and set the code:

function onSubmit() {

	//Choices variables concerned

	var application_alert = g_form.setDisplay(alert_application, 'true');
	


	// Option PRODUCTION is selected and at least one of the conditions is true
	if( application_alert){}

//here's the code to condition the Attachment mandatory
}

Thanks