This example creates a balloon that generates an error. The error is generated because the balloon is created without a way to dismiss it: the button type is set to msoButtonSetNone and the default balloon mode is msoModeModal, resulting in a buttonless, modal balloon. Note that there's no way to dismiss a buttonless modal balloon.
With Application.Assistant
With .NewBalloon
.Heading = "This will never show."
.Text = "Imagine a balloon here."
.Button = msoButtonSetNone
.Show
End With
.Visible = True
If .BalloonError = msoBalloonErrorButtonlessModal Then
MsgBox "You need a button to dismiss the balloon."
End If
End With