Clearing a part of the window

Hello everyone…
Im very new to OpenGl…Im sorry, this question sound trivial…But i really need ur help…

How can i clear only a part of the graphics window??
I changed the viewport to that required area and tried clearing it…it did not work…

Bsically i want to clear it so as to display text info…ie display text,clear that part display some other info…
Pls help…
Thanks in advance.

You have to swap the buffers wglSwapBuffers after cleaning each viewport…as with rendering.

Check this wiky regard the multiple viewports:
http://www.opengl.org/wiki/Viewing_and_T…e_same_scene.3F

The reference to scrissor function is here:
http://www.opengl.org/sdk/docs/man/xhtml/glScissor.xml

Try to put the two commands before invoke glClear(…)
glScissor(x, y, width, height);
glEnable(GL_SCISSOR_TEST);

Its still not working…I gave glClear() after giving glScissor()…

This is what im doing.Pls tell me if im right…

glScissor(500, 500, 70, 20);
glEnable(GL_SCISSOR_TEST);
    glClearColor(1.0,1.0,1.0,0.0);
glClear(GL_COLOR_BUFFER_BIT); 

What im doing is basically a graphics editor…
So i display “help” regarding some drawing tool and then when the cursor goes on another tool,the “help” info is changed wrt the new tool.So im required to clear only that small part of the window where the help is being displayed…How can i do this??