Before an OCX can be used, it must be registered with the System Registry. Suppose the OCX you want to use is called "test.ocx". To register this OCX use code from example below. You can the same way unregister the OCX: all you have to do is to replace 'DllRegisterServer' by 'DllUnregisterServer'. You should add some validation code: "Does the file exist", "Was the call to LoadLibrary successful?", ... Some explanations: An OCX is a special form of dll, so you can load it in memory with a call to the LoadLibrary API function. An OCX exports two functions to register and unregister the control. You then use GetProcAddress to obtain the address of these functions. You just have then to call the appropriate function. And that's it! You can explore the Registry (with regedit.exe) to verify that the OCX is registered.
var OCXHand: THandle; begin OCXHand:=LoadLibrary('c:\windows\system\test.ocx'); if (GetProcAddress(OCXHand,'DllRegisterServer')<>nil) then ShowMessage('Error!'); FreeLibrary(OCXHand); end;