Hello Kimmo,
You can do this using the 'Meter' numeric control (rather than the Gauge). You will use the Scale.MarkerVals[] property.
See attached VI for a demo. I am using the vertical slider only to change the value. The VI is saved in 7.1 version. If you have an older version, see the attached screenshot.
Hope this is what you were trying to accomplish.
Regards,
Khalid