Cancelar validación de un campo en un Formulario AX 365

[FormControlEventHandler(formControlStr(SalesTable, SalesLine_ItemId), FormControlEventType::Validated)]
public static void SalesLine_ItemId_OnValidated(FormControl sender, FormControlEventArgs e) {

    boolean allow = true;
    FormControlCancelEventArgs FormControlCancelEventArgs =  e as FormControlCancelEventArgs;
    FormStringControl FormStringControl_ItemId = sender as FormStringControl;

    allow =  ///rutina para determinar si se debe cancelar o no.

   if(allow == false)
   {
       args.cancel(true);
   }

 }