Private Declare Function GetAsyncKeyState Lib "user32" (ByVal vKey As Long) As Integer
Private Sub ComboBox1_KeyDown(ByVal KeyCode As MSForms.ReturnInteger, ByVal Shift As Integer)
If KeyCode = 9 Then If GetAsyncKeyState(16) Then ComboBox4.Activate Else ComboBox2.Activate
End Sub
Private Sub ComboBox2_KeyDown(ByVal KeyCode As MSForms.ReturnInteger, ByVal Shift As Integer)
If KeyCode = 9 Then If GetAsyncKeyState(16) Then ComboBox1.Activate Else ComboBox3.Activate
End Sub
Private Sub ComboBox3_KeyDown(ByVal KeyCode As MSForms.ReturnInteger, ByVal Shift As Integer)
If KeyCode = 9 Then If GetAsyncKeyState(16) Then ComboBox2.Activate Else ComboBox4.Activate
End Sub
Private Sub ComboBox4_KeyDown(ByVal KeyCode As MSForms.ReturnInteger, ByVal Shift As Integer)
If KeyCode = 9 Then If GetAsyncKeyState(16) Then ComboBox3.Activate Else ComboBox1.Activate
End Sub