There are links on the Flash Magic web page to several useful documents.

http://www.keil.com/lpc/me900.chm contains the schematic diagram of the Keil MCB900. You can use this to program an LPC9xx that supports ISP. Alternatively you can program an LPC932 or LPC935 as an ISP to ICP bridge and use it in this circuit.

http://www.esacademy.com/software/flashmagic/resources/prog90x.zip is the ISP to ICP bridge code.

http://www.esacademy.com/software/flashmagic/appnotes/ISPHardwareEntryAppNote.pdf describes how the Keil MCB900 circuit works.

http://www.esacademy.com/software/flashmagic/resources/AN10258_2.pdf describes how to use the Keil MCB900 circuit to program LPC9xx devices that support ICP.

Hope this helps.

Andy