How can I manage several GL contextS with TinyGL

It seems that we start MiniGL with something like this

TinyGLBase = OpenLibrary("tinygl.library", 0);
tgl_context=GLInit();
glAInitializeContextBitMap(tgl_context,bm);

But if I want to have several contexts: context1 context2 in a same binary (*) (contexts that use differents bitmaps ) then How can I choose the current context so a (say)
glClear(GL_COLOR_BUFFER_BIT);
will took effect on context2 not context1

To select a context Windows got this fonction
wglMakeCurrent (hdc,hglrc);
And ArosMesa got this one
AROSMesaMakeCurrent(ctx);

But what is the "Select a given GL context" function in TinyGL ????

Many Thanks

Alain Thellier

(*) In fact it is for Wazp3D. Wazp3D truly need to manage several GL contexts