Could you put the code you used in the rowdatabound cause this best getway to do what ever you want , here an Ex:
protected void OnRowDataBound(object sender, EventArgs e)
{
GridViewRowEventArgs ea = e as GridViewRowEventArgs;
if (ea.Row.RowType == DataControlRowType.DataRow)
{
DataRowView drv = ea.Row.DataItem as DataRowView;
Object ob = drv["Phone"];
if (!Convert.IsDBNull(ob))
{
Int64 iParsedValue = 0;
if (Int64.TryParse(ob.ToString(), out iParsedValue))
{
TableCell cell = ea.Row.Cells[4];
cell.Text = String.Format(System.Globalization.CultureInfo.CurrentCulture,
"{0:(###) ###-####}", new object[] { iParsedValue });
}
}
}
}