External microphone for Transcend T.sonic 630

Hi friends,
3 days ago i buy a mp3 player transcend t.sonic 630. This mp3 had option to plug external mic to the line-in and after configure in the menu you may record voice with this ext. mic.
So i need the schematic of creating with my own hands external mic.And schematic must contain the connection to mp3 player using 3,5 mm stereo jack. Please help.
Best regard Linoko

Sorry about my English

Can't you buy an external microphone?

I wouldn't have thought there is a circuit, just plug a dynamic microphone in and it should work.