Please extend the parent of your tab :) :
1. Its message map:
ON_REGISTERED_MESSAGE(AFX_WM_ON_GET_TAB_TOOLTIP, OnTabToolTipNeeded)
2. Its function:
LRESULT CYourFrame::OnTabToolTipNeeded(WPARAM wParam, LPARAM lParam)
{
if (m_cTabCtrl.GetSafeHwnd()) {
CMFCTabToolTipInfo* pcInfo = (CMFCTabToolTipInfo*) lParam;
if (pcInfo) {
CString cszText;
if (m_cTabCtrl.GetTabLabel(pcInfo->m_nTabIndex, cszText) &&
cszText.GetLength()) {
CYourView* pcView(DYNAMIC_DOWNCAST(CYourView, m_cTabCtrl.GetTabWnd(pcInfo->m_nTabIndex)));
if (pcView->GetSafeHwnd()) {
cszText += _T(" [");
cszText += pcView->GetPath();
cszText += _T("]");
}
pcInfo->m_strText = cszText;
}
}
}
return 0;
}