There aren't functions in CVI for this. You would do it through Windows SDK functions. The function you would use would be GetSystemMenu, then you could use the WinSDK menu functions (InsertMenuItem, etc.) on the menu handle returned to add things to the system menu. You would need to get the hWnd for your CVI panel which you can get with GetPanelAttribute on the System Window Handle. Consult the Windows SDK help from CVI's help menu to find out about these functions. If thes SDK help isn't there, you may need to re-install CVI and add the Windows SDK to your install.
Best Regards,
Chris Matthews
National Instruments