If you want to retain the styling and formatting of the GridPanel, it will be hard. However, if you are only looking for a data dump export, you can easily export your datasource as a csv file to Excel.
Public Shared Sub ExportDataTable(ByVal aDataTable As DataTable, ByVal aWriter As IO.TextWriter)
Dim colCount As Integer = aDataTable.Columns.Count
'add column headers
For Each column As DataColumn In aDataTable.Columns
aWriter.Write(column.Caption & ",")
Next
aWriter.WriteLine()
'add cells
For Each row As DataRow In aDataTable.Rows
For i As Integer = 0 To colCount - 1
aWriter.Write(row(i).ToString.Replace(",", String.Empty) & ",")
Next
aWriter.WriteLine()
Next
End Sub