Put your instructions in the TextBox as either the default or in the UserForm_Initialize event. Then put the following code for your TextBox:
Private Sub TextBox1_MouseDown(ByVal Button As Integer, ByVal Shift As Integer, ByVal X AS Single, VyVal Y As Single)
With TextBox1
.SelStart = 0
.SelLength = Len(.Text)
End With
Selection.ClearContents
End Sub
Did that do the trick