In order to hide/show controls on the form, we can either use the "Visibility Formula" which is inside the control properties window in the designer, or write some script to perform the same action.
Examples :
form.GetControl("c_Status") != "Rejected"
form.UserID() == "1" || form.UserInGroup("Administrators") || form.UserInGroup("3")
Inside the Value-Change event of the "c_Customer" control :
var target = form.GetControl("c_Priority");
var source = form.GetControl("c_Customer");
if (source.GetValue() == "1;#BPC") target.SetVisible(false);
else target.SetVisible(true);