A set of custom controls are available for use in the user interface design of 3ds Max plugins. The 3ds Max program itself makes extensive use of these custom controls. These controls provide an important element of consistency between the plug-in and the system, making new plugins appear fully integrated with 3ds Max. The use of these controls by the majority of developers will provide a level of familiarity for users who often work with many different plugins.
The sample program CUSTCTRL.CPP demonstrates each of the custom controls which may be used in the command column. To run this program, copy the \\MAXSDK\\PLUGIN\\CUSTCTRL.DLU file into the stdplugs folder of the 3ds Max installation directory, and the corresponding \\MAXSDK\\PLUGIN\\CUSTCTRL.DLU.MUI file into the appropriate language sub-folder, that is stdplugs\\en-US. The program is implemented as a utility plug-in. You can run the program by choosing the Custom Control selection in the Utility branch under How To. This section makes reference to portions of this plug-n.
You can also look at the custom controls header file custcont.h.