Dialog Based App and CToolBar

I have a dialog based app that I have added a toolbar. I have the ON_COMMAND events working but can not get the ON_UPDATE_COMMAND_UI events to fire. I would like the three toolbar buttons to act as radio buttons where only one of the three is checked.
I have a variable called m_uCurrentBtn (UINT) which is set to the button ID in the ON_COMMAND event. I am trying to set the button state using:

pCmdUI->SetRadio(pCmdUI->m_nID == m_uCurrentBtn);


But I can not get the event to fire. What am I missing.



Thanks,
Robert