من پیشنهاد می کنم از رویداد KeyDown فرم استفاده کنی و ...
Public Class Form1
Dim GBox As Int16 = 1
Private Sub Form1_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyDown
' Dont Forget : Set Me.KeyPreview = True !!!
If e.KeyData = Keys.F5 Then
Select Case Me.GBox
Case 1
Me.TextBox4.Focus()
Case 2
Me.TextBox1.Focus()
End Select
EndIf
End Sub
Private Sub GroupBox1_Enter(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles GroupBox1.Enter
GBox = 1
EndSub
Private Sub GroupBox2_Enter(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles GroupBox2.Enter
GBox = 2
End Sub
End Class
ببخشید بر اثر Copy/ Paste بعضی از واژه های کد ممکنه بهم چسبیده باشه. اصلاح کنیدش