setKey(<nKey> [, <bBlock>]) --> bPrevious

        Gets and optionally sets the code block indicated by <bBlock> that is
        associated with the Inkey value specified by <nKey>.  When replacing
        an existing keypress/code block definition, it returns the previous
        code block; otherwise, it returns the current one.

        TBrowse:SetKey() Default Keypress/Code Block Definitions
        ---------------------------------------------------------------------
        Inkey Value    Associated Code Block
        ---------------------------------------------------------------------
        K_DOWN         { | oTB, nKey | oTB:Down(), TBR_CONTINUE }
        K_END          { | oTB, nKey | oTB:End(), TBR_CONTINUE }
        K_CTRL_PGDN    { | oTB, nKey | oTB:GoBottom(), TBR_CONTINUE }
        K_CTRL_PGUP    { | oTB, nKey | oTB:GoTop(), TBR_CONTINUE }
        K_HOME         { | oTB, nKey | oTB:Home(), TBR_CONTINUE }
        K_LEFT         { | oTB, nKey | oTB:Left(), TBR_CONTINUE }
        K_PGDN         { | oTB, nKey | oTB:PageDown(), TBR_CONTINUE }
        K_PGUP         { | oTB, nKey | oTB:PageUp(), TBR_CONTINUE }
        K_CTRL_END     { | oTB, nKey | oTB:PanEnd(), TBR_CONTINUE }
        K_CTRL_HOME    { | oTB, nKey | oTB:PanHome(), TBR_CONTINUE }
        K_CTRL_LEFT    { | oTB, nKey | oTB:PanLeft(), TBR_CONTINUE }
        K_CTRL_RIGHT   { | oTB, nKey | oTB:PanRight(), TBR_CONTINUE }
        K_RIGHT        { | oTB, nKey | oTB:Right(), TBR_CONTINUE }
        K_UP           { | oTB, nKey | oTB:Up(), TBR_CONTINUE }
        K_ESC          { | oTB, nKey | TBR_EXIT}
        K_LBUTTONDOWN  { | oTB, nKey | tbMouse(oTB, MROW(), MCOL()) }
        ---------------------------------------------------------------------

        Key handlers may be queried, added, replaced, and removed from the
        dictionary.  For example:

        oTB:SetKey(K_ESC, { | oTB, nKey | TBR_EXIT })

        A default key handler may be declared by specifying a value of 0 for
        <nKey>.  Its associated code block will be evaluated each time
        TBrowse:ApplyKey() is called with a key value that is not contained
        in the dictionary.  For example:

        oTB:SetKey(0, { | oTB, nKey | DefTBProc(oTB, nKey) }

        The example above calls a function named DefTBProc() when nKey is not
        contained in the dictionary.

        To remove a keypress/code block definition, specify NIL for <bBlock>.
        For example:

        oTB:SetKey(0, NIL }