Mac OS X uses a fixed non user changeable System Font. This format is '.dfont' a Macintosh TrueType suitcase. However Snow Leopard is now using this 'ttc' format.
The workaround currently being used is to open the System font which contains Regular and Bold typefaces and the desired custom font in both regular and bold. Fontlab Studio provides the ability to merge the custom font typefaces into the System font which finally is exported as a Macintosh TrueType '.dfont'. In a way this tricks the system to display a custom themed font
However Snow Leopard, the latest version of Mac OS X is now using this Microsoft Windows 'ttc' TrueType Font collection format. Unfortunately Fontlab cannot open this format and cannot export to it. There seems nothing else on the Mac platform that I can find. I thought I'd broaden the range and look far afield in the Windows domain for a tool to accomplish this. I find it ironic there is nothing on this platform either considering the '.ttc' to be a Microsoft format. Strange