You could try something like this (you must obtain the long HWND for the window you want to activate):-

#define SW_HIDE 0
#define SW_SHOWNORMAL 1
#define SW_NORMAL 1
#define SW_SHOWMINIMIZED 2
#define SW_SHOWMAXIMIZED 3
#define SW_MAXIMIZE 3
#define SW_SHOWNOACTIVATE 4
#define SW_SHOW 5
#define SW_MINIMIZE 6
#define SW_SHOWMINNOACTIVE 7
#define SW_SHOWNA 8
#define SW_RESTORE 9
#define SW_SHOWDEFAULT 10
#define SW_MAX 10

declare integer ShowWindow in win32api LONG HWND, INTEGER CmdShow

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ShowWindow(lnHWND, SW_RESTORE)