display resolution on my thinkpad t61

[Alokat]

Hi,

I'm trying to modify my screen resolutions (use an external and the 
internal monitor).

xrandr -q says:

Screen 0: minimum 320 x 200, current 1440 x 960, maximum 2720 x 1024
VGA connected 1440x900+0+0 (normal left inverted right x axis y axis) 
408mm x 255mm
    1440x900       59.9*+   75.0
    1280x1024      75.0     60.0
    1280x960       60.0
    1152x864       75.0
    1024x768       75.0     70.1     66.0     60.0
    832x624        74.6
    800x600        72.2     75.0     60.3     56.2
    640x480        75.0     72.8     66.7     66.0     59.9
    720x400        70.1
LVDS connected 1280x960+0+0 (normal left inverted right x axis y axis) 
331mm x 207mm
    1280x1024      85.0     75.0     60.0
    1280x960       85.0*    60.0
    1152x864       75.0
    1024x768       85.0     75.0     70.1     60.0
    832x624        74.6
    800x600        85.1     72.2     75.0     60.3     56.2
    640x480        85.0     72.8     75.0     59.9
    720x400        85.0
    640x400        85.1
    640x350        85.1
TMDS-1 disconnected (normal left inverted right x axis y axis)

1440x900 is enough for the external but the internal can / should use 
1680x1050.
How can I add this to xrandr?

Regards,
alokat