There is a special section in the control properties dialog where users can write the client-side script that will be executed when the value for that control changes.
All the available methods and properties of the "form" object or the individual control methods can be found here :
Control properties and methods
The Value-Change event of each control is raised every time the value of that control changes due to :
In order to determine if the change is due to the initialization of the form, the "form.Loaded" property should be used.
For example :
var value = form.GetControl("c_Status").GetValue();
if (form.Loaded) {
if (value == "Closed") form.GetControl("c_Progress").SetValue("100");
}