>>>>>>I want to give to my forms a more user friendly interface, I want to enabled my forms to change position to controls when the user is left-handed, because I think that with a left-handed mouse it's more difficult to click on some position than with a right-handed mouse. So how can I know if the user have setted in control panel the left-handed mouse ?

>>>>PMFJI, but I have to ask: Isn't this a function of the OS? If I go to the Control Panel and tell Win95 to swap mouse buttons (switch from right-handed to left-handed) can an application tell the difference? That is, if I've switched to left-handed mode and left-click a button, doesn't it show up as a plain 'click' to the app?

>>>Yep, this is a function of the OS. However, Windows handles the mouse clicks through its messaging services. If the mouse buttons are swapped, the application doesn't know, but responds in the proper manner. IOW, if the mouse is set up to be left-handed and you click the left mouse button, the application will react as it would if the mouse was set up as right-handed, and the right mouse button was clicked.

>>I think that was exactly Paul's point. Instead of referring to them as left and right mouse buttons, let's call them the primary and secondary mouse buttons (primary is left for righties, etc.). In that case if your application is checking for PrimaryButtonDown it won't matter if a rightie pushed the left button or a leftie pushed the right button the application will be notified correctly. This means there is no reason for an application to query regarding the swapped nature of the mouse buttons unless the purpose of the app is to swap the buttons.

>I wonder if this falls into the category of being "Politically Correct"?< g >

Actually, I miss read the original post. I thought the question was concerning trapping the left-click as a right-click when, in fact, the question was about rearranging the controls on a form for greater convenience to a left-handed person.
Oddly enough, I did bring up a good point (inadvertently) about "right button" usually being synonymous with "primary button". A fact which carries over into the VFP IDE (the Event *is* called .RightClick).