Hi all,
I'm working on a financial form that is filled out and then a pdf is outputted (via php).

I'm an xhtml/css and php guy but new to javascript - I'm sure there's got to be a way to do the following with js...

I've got a section for "project costs" with 4 fields (numeric is expected). I'd like to add a 5th field "Total Project Cost" that adds all the inputs of the first 4 fields on the fly as they are typed (or at least, after focus changes).

Also I'd like to have a field which defaults to "10" and a drop down with 3 items that will either add 0, 5 or 10 to the field which defaults to 10.

Can anyone recommend a script or js library that can handle these "on the fly" calculations? I appreciate the help - Thank you!