Select and MAINTAIN the aspect ratio

Greetings, I have a Dell 2407WFP, and sometimes I use an application that have some screen at  1024x768 and some at 1920x1200. When the resolution is 1024, I can use the monitor display settings in order to maintain the aspect ratio, so I have two lateral black bars and no image distortion. The problem is that I have to select this setting every time I use that application, so the question is: is there a method to "save" the setting and have the aspect ratio maintained every time?

Thank you.