that can be done with Fontographer..you need that software to make your own font..but first you have a lot of work to do..sketch your font from A-Z,0-9 and trace it..using AI..and then you can use the Fontographer..I guess that's the way..I don't really know there's any other way..
There is also Fontlab, Fontographer's bigger brother. You might also look in Scanfont which allows you to scan in your hand drawn font and it does a pretty good job of auto-tracing it for you. However, creating an entire font with all characters and proper kerning and ligatures is no small task. I recommend that you join http://www.typophile.com/ , the people on here do nothing but talk about type and are very eager to help a budding type designer. There is also this http://www.pentacom.jp/soft/ex/font/edit_canvas.html , which is a free bitmap font creator.