Why MDI Child not gaining focus after user returns from Form.ShowDialog()

See more:

VB

Here Is My Code For Textbox_KeyDown

Private Sub TxtOrderNo_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TxtOrderNo.KeyDown
        If e.KeyCode = Keys.F4 And Me.Tag = "View" Then
            frmhelp = New FrmHelp
            frmhelp.Sql = "SELECT SalesOrderMast.OrderNo AS [ORDER NO], SalesOrderMast.OrderDate AS [ORDER DATE], PARTYMASTER.Description AS [PARTY NAME] FROM SalesOrderMast" & vbCrLf _
            & " LEFT JOIN SUBLEDGERMASTER AS PARTYMASTER ON SalesOrderMast.PartyCode = PARTYMASTER.SubLedgerCode ORDER BY SalesOrderMast.OrderNo"
            frmhelp.TxtObject = TxtOrderNo
            frmhelp.ReturnField = 0
            frmhelp.OnLineCreationYN = False
            frmhelp.Gridsize1 = {100, 100, 300}
            frmhelp.HelpTitle = UCase("Order No")
            frmhelp.Top = 300
            frmhelp.Left = 350
            frmhelp.ShowDialog()
            frmhelp = Nothing
            Call TxtOrderNo_Validating(Nothing, Nothing)
        ElseIf e.KeyCode = 13 Then
            Call TxtOrderNo_Validating(Nothing, Nothing)
        End If
    End Sub

Return Value From frmhelp Form
When Working With Same Mdi Application its Work Perfect But
When Sql Server Management Studio Query Window Execute Query
Then Focus Move To the Sql Server Management Studio Query Window
Same Thing happens with any Other Application Like Excel, Word

Please Help Me
Thanks In Advance

Please Find Attachment

https://drive.google.com/file/d/0B3fvL_S8Z_DbRm9XVEFwbnJqWVU/view[DownLoad Code]