Prueba esta forma:
****************************************
*OCULTAR BARRA DE TAREAS
Declare Integer FindWindow In
"user32" As "FindWindowA" ;
String lpClassName, ;
String lpWindowName
Declare Integer SetWindowPos In
"user32" ;
Integer hwnd , ;
Integer hWndInsertAfter , ;
Integer x ,;
Integer y , ;
Integer cx ,;
Integer cy ,;
Integer wFlags
Ventana = FindWindowA("Shell_traywnd","")
=SetWindowPos (Ventana, 0, 0, 0,0, 0, 128 ) && oculta
Wait window time 1
=SetWindowPos (Ventana, 0, 0, 0, 0, 0, 64) && muestra
****************************************************************