Mfc..how to change font of string with menu button

[vatralaus]

I am haveing problem changing font of the displayed text.
it is MFC aplication.
In the big white window "not dialog" we can see just text (just simple string object) lets say """CODE GURU""".so what i whant is to create simple toolbox button and when i press it """CODE GURU""" text that is already displayed to change font.
Here is my button action.

ON_COMMAND(ID_EDIT_FONT, &CFesbView::OnEditFont)

void CFesbView::OnEditFont()
{
CFesbDoc* pDoc = GetDocument();

//this is my button action.
//so what woud go here


Invalidate();
}