Which version of Excel are you using? I've just put a command button on a multipage and assigned a ControlTipText to it. It showed up when I hovered the mouse over it. I also changed it at runtime by using this code in the form's code module:-
Private Sub UserForm_Initialize()
Me.CommandButton1.ControlTipText = "Hello"
End Sub
Are you saying that even if you assign something to the ControlTipText even at design time, then you do not see the tip when you hover the mouse over the command button? I'm using Excel 2000. Can you post a description of your form (I'm assuming the multipage control is on a form and not on another object such as a worksheet) along with all code in the form. There may be something else which is preventing the tip text from showing.
Regards,
Dan