If the application was created by an employee on the job, the source code belongs to the company unless he had an agreement. You should ask around, look around, poke around and try to find it. If you just want to make some changes, that would be the very best place to start, regardless of what language it's written in.
But starting from scratch for something like that would probably best be done in a scripting language as Delloch suggests. Python
seems to have taken the world by storm.
But there is one other solution you might consisder: NSIS (Nullsoft Scriptable Install System)
. When you install an application on Windows, you often run setup.exe, which opens a series of standard-looking windows to gather information and guide you through installation. Some of those have no-doubt been created with NSIS. You can make a really nice looking installer with a relatively small script. It's free.
The downside of NSIS is that the language is very non-intuitive, at least I think so, which means a steep learning curve.