Could you help me with my code

this error

sub showPinDialog()
    m.pinDialog = createObject("roSGNode", "PinDialog")
    m.pinDialog.title = "Example  Pin Dialog"
    'm.pinDialog.optionsDialog = true
    m.pinDialog.message = "Press * To Dismiss"
    m.pinDialog.buttons = ["Ok","Cancel"]
    m.top.dialog.observeFields("buttonSelected","onVerifyPin")
    m.top.dialog = m.pinDialog
End sub

Function onVerifyPin()
    m.userpin = m.top.dialog.pin
	print m.userpin
    if m.top.dialog.buttonSelected = 1
       print "ok button pressed"
    else
       print "cancel button pressed"
	  m.top.dialog.close = true
    end if
end Function

146:*     m.top.dialog.observeFields("buttonSelected","onVerifyPin")