Advice on selling an app

I created a very small application that's only useful in my industry. It is a single .exe file so it is easily copied and shared.

I added the logo/trademark info of the company I work for as it was to be used by us internally. I was asked if I could change the logo and info for someone working at a different company.

Should I change for this service? How much would be appropriate? It's a small app, but is a huge time saver and I know will be distributed around the company. Are there any legal matters involved if I charge for it?

Any thoughts on the matter are appreciated!