XPSP4, Excel 02, custom button to SEND MESSAGE wont stay on toolb
 

When attempting to add custom button (Mail Recipient) to standard toolbar,
the button will only display temoraily, until the CLOSE button is clicked on
the CUSTOMIZE dialog box. XP Pro SP2, Excel 2002 SP3. What might be
preventing the button from staying on toolbar. Logged in as administrator on
local box. Local copy of Excel.