How to incrementally save images using a hotkey

Question

What I'm hoping to accomplish is as follows:
Draw a line, then
Press a hotkey to Play an Action.
     The action needs to save an incremental .jpeg
     and then select the previous history state.
The goal being that everytime I try to undo a mark, I have a copy of the image with the mistake, creating a record of the process. I have absolutely no knowledge of scripting. I will basically use this as an alternative undo key.
I am working on a project in which I need to save "snapshots" of my progress. Basically I'm working on a digital sketchbook and am trying to record the progress of every mark I make on the page. My workflow for this project entails the drawing of a line and then selecting of the previous history state, erasing the lines I do not want and layering the ones I do. The idea being that I can catologue my entire workflow and progress in a series of images to post to my sketchbook blog. This is part of a longterm project to track improvement and I'm am following this ideal for multitudes of images each day.
I suppose all I'm asking for here is a script that will run and save a .jpeg of the current .psd, adding a "_001, _002, _003" suffix to the filename, checking to see if the current suffix is taken and changing to the next one. This way I can catalogue the "snapshots" of mutiple images in the same folder.
Using Photoshop CS5 on OSX Snow Leopard.

Answer 1

Try this....
#target photoshop
main();
function main(){
if(!documents.length) return;
var Name = app.activeDocument.name.replace(/\.[^\.]+$/, '');
try{
var savePath = activeDocument.path;
}catch(e){
    alert("You must save this document first!");
var fileList= savePath.getFiles(Name +"*.jpg").sort().reverse();
var Suffix = 0;
if(fileList.length){
    Suffix = Number(fileList[0].name.replace(/\.[^\.]+$/, '').match(/\d+$/));
Suffix= zeroPad(Suffix + 1, 3);
var saveFile = File(savePath + "/" + Name + "_" + Suffix + ".jpg");
SaveJPEG(saveFile, 8);
function SaveJPEG(saveFile, jpegQuality){
jpgSaveOptions = new JPEGSaveOptions();
jpgSaveOptions.embedColorProfile = true;
jpgSaveOptions.formatOptions = FormatOptions.STANDARDBASELINE;
jpgSaveOptions.matte = MatteType.NONE;
jpgSaveOptions.quality = jpegQuality;
activeDocument.saveAs(saveFile, jpgSaveOptions, true,Extension.LOWERCASE);
function zeroPad(n, s) {
   n = n.toString();
   while (n.length < s)  n = '0' + n;
   return n;