[OpenLayers-Users] Can I constrain a map to a certain scale in pixels/km?

[Nick Whitelegg]

I'm developing a "slippy map" based on OpenStreetMap with SRTM contours. I 
have pre-generated a set of 500x500 tiles of scale 100 pixels/km using 
Mapnik. My maps are in OSGB projection: the bounding box requests are in 
metre units.

With OpenLayers am I able to constrain the map to a certain number of 
pixels/km e.g. either 100 or 200 (they are the scales I intend to support)?

Thanks,
Nick