[racket] plot pixel position

Plot is fantastic - thanks so much!

Is there a way to hook into the interactive features of plot so, for 
instance, the user could click to add data or drag data points around?

I'm using plot/dc to draw onto a canvas, and I'd be more than happy just 
to be able to ask a plot to translate a pixel position to the 
corresponding axes' positions.  I know that plot does this for the 
zooming feature, but is there a way for external code to do it?

Thanks,
Dave