Sending non-string parameters to an AppleScript

FROM : Jeremy Dronfield
DATE : Sun Jul 23 16:58:41 2006

I'm calling an AppleScript using NSAppleScript and 
NSAppleEventDescriptor. Part of the the purpose of the script is to 
set the positions of the icons in a Finder window. My problem is in 
working out how to pass a parameter (in this case a point) which 
isn't an NSString, since +[NSAppleEventDescriptor 
descriptorWithString:] seems to be the only way of passing an Obj-C 
data type. In desperation I've tried using:

[NSAppleEventDescriptor descriptorWithString:NSStringFromPoint
(NSMakePoint(100, 100))]

and coercing the parameter to a point in the script with:

set position of item fileRef of windowRef to (newPosition as point)

but it doesn't work. I get an error: "{100, 100}" cannot be converted 
to type point. Surely it must be possible to pass a point (and other 
data types) to an AppleScript? If so, how?

Jeremy