We have one application which works with AutoCAD 2011. The application is build in VBA and VB technology. Our application is a tool bar functionality in AutoCAD 2011. The issue is "When we open userform from AutoCAD it is opening in background". We are using Auto CAD 2011 and Windows 7, but for Auto CAD 2009 or WinXP we don't have that issue.
You may need to download and load the VBA add-on from AutoDESK. The VBA apps tool was removed in 2011. If this is not it you may need to post in the VBA forum to get the answer you are looking for.