C#

private void Grid_CellParsing(object sender, DataGridViewCellParsingEventArgs e)
   {
       if (this.dgvInvoice.Columns[e.ColumnIndex].Name == "DateColumn")
       {
           try
           {
               e.Value=customfunction(e.Value);
           }
           catch
           {
               e.Value = DateTime.Today;
           }
       }

       e.ParsingApplied = true;
   }