public static QuarterlyProfitLossFrm GetInstance()
 {
     if (singleton == null)
     {
         singleton = new QuarterlyProfitLossFrm();
     }
     return(singleton);
 }
 private void QuarterlyProfitLoss_FormClosed(object sender, FormClosedEventArgs e)
 {
     singleton = null;
 }