I think this is what you're after,
Add a command button and a textbox to form1

Option Explicit

Private Sub Command1_Click()
Dim Result As VbMsgBoxResult

Result = MsgBox("Would you like to set the focus to the textbox?", vbQuestion + vbYesNo, "Set Focus")
If Result = vbYes Then
Text1.SetFocus
End If
End Sub