Create a hidden field in your form and add a rule, e.g, if the hidden field
is blank then hide another control else display it. The hidden field will
always be blank by default so your control will be disabled when the form
loads. You can also do this programmatically:

   public void InternalStartup()
       {
           EventManager.FormEvents.Loading += new
LoadingEventHandler(FormEvents_Loading);
         
}

 private void FormEvents_Loading(object sender, LoadingEventArgs e)
       {
 XPathNavigator _DOM = this.MainDataSource.CreateNavigator();
           XPathNavigator Option =
_DOM.SelectSingleNode("/my:myFields/my:yourfieldname", this.NamespaceManager);
     
Option.SetValue("anyvalue");
}

This code will set the hidden field's value which will enable the button
according to the rule that you applied in your form. Similarly, you can clear
the field to disable the button.

Hope this helps

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