First you need to create a project file with the following control

lblTest (Label)
txtEdit (Text Box)

and the code will look like below:

Code:
Option Explicit
Private Sub lblTest_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
'only apply to mouse's left button
If Button = vbLeftButton Then
    txtEdit.Top = lblTest.Top
    txtEdit.Left = lblTest.Left
    txtEdit.Height = lblTest.Height
    txtEdit.Width = lblTest.Width
    txtEdit.Text = lblTest.Caption
    txtEdit.Visible = True
    If lblTest.Caption <> "" Then
        txtEdit.SelStart = Len(lblTest.Caption)
        txtEdit.SetFocus
    End If
End If
End Sub

Private Sub txtEdit_KeyPress(KeyAscii As Integer)
If KeyAscii = 13 Then
    lblTest.Caption = txtEdit.Text
    txtEdit.Visible = False
End If
End Sub

Private Sub txtEdit_LostFocus()
txtEdit.Visible = False
End Sub