Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs)
    AddHandler GcMultiRow1.PopupCellOpeningForm, AddressOf GcMultiRow1_PopupCellOpeningForm
End Sub
                                                        
Private Sub GcMultiRow1_PopupCellOpeningForm(ByVal sender As Object, ByVal e As GrapeCity.Win.MultiRow.PopupCellOpeingFormEventArgs)
    Dim isOdd As Boolean = (e.RowIndex Mod 2) = 0
    e.Popup = If(isOdd, GetType(ColorDialog), GetType(MyDialog))
    e.PopupValueMember = If(isOdd, "Color", "VText")
End Sub 
private void Form1_Load(object sender, EventArgs e)
{
    gcMultiRow1.PopupCellOpeningForm += GcMultiRow1_PopupCellOpeningForm;
}
                                                        
private void GcMultiRow1_PopupCellOpeningForm(object sender, GrapeCity.Win.MultiRow.PopupCellOpeingFormEventArgs e)
{
    var isOdd = e.RowIndex % 2 == 0;
    e.Popup = isOdd ? typeof(ColorDialog) : typeof(MyDialog);
    e.PopupValueMember = isOdd ? "Color" : "VText";
}