[OpenLayers-Users] change WMS parameter on refresh

[Charles Galpin]

This is probably really simple but I'm drawing a blank. 

I have a OpenLayers.Layer.WMS layer that I want to change a parameter each time it refreshes (on initial load, zoom, explicit refresh, whenever). In case you are curious ultimately I want to pass the map scale as part of  a parameter called "viewparams" which allows one to pass parameters to geoserver sql views. I can send a static value just fine from the value provided for params during construction, but need to make it dynamic.

So perhaps there is a pre-load event handler I can add to do the equivalent of mergeNewParams say? Thoughts?

Thanks,
charles