Private Sub Form_Load()
    Command1.TabStop = False
End Sub

Private Sub Text1_KeyDown(KeyCode As Integer, Shift As Integer)
    If KeyCode = vbKeyTab And Len(Text1.Text) = 6 Then
        Command1.Value = True
    End If
End Sub

Private Sub Command1_Click()
    MsgBox "因为 Tab 会将 focus 移到物件上" & _
            vbCrLf & "而无法触发事件；在适当时候加入" & _
            vbCrLf & "物件.TabStop = False 即可解决!"
End Sub

Private Sub Form_Load()
    Text1.TabIndex = 0
    Command1.TabIndex = 1
End Sub
Private Sub Text1_Change()
If Len(Text1.Text) = 6 Then
        Command1.Value = True
  End If
End Sub
Private Sub Command1_GotFocus()
    If Len(Text1.Text) <> 6 Then Exit Sub
    Command1.Value = True
End Sub
Private Sub Command1_Click()
    MsgBox "Form 上有多个物件的另一种解法，供大家参考"
End Sub