is there a way to pass arguments to google map’s get directions functionality?

You can use the following url parameters.

saddr for start address

daddr for destination address

The url would be http://maps.google.com/maps?saddr=new+york&daddr=baltimore

The values you pass in can be pretty much whatever you can type into the web app, ie names of places/lat longs/etc. Also, make sure you use a + character for spaces.