Generate Code of dlls..

Hello sir,
I am in Trouble now . last Month i develop a project and create a dll

of that and SOME TIME LATER I LOST MY PROJECT CODE.nOW ANOTHER CLIENT

ASK FOR DEMO OF THE SAME PROJ I CREATED WITH SOME MODIFICATIONS.bUT HOW

CAN I MAKE MODIFICATION WITH MY PROJ WITHOUT CODE.

Only one way is recall my code use dlls.But How.

Please give me suggestion to generate code.
please tell me fast.