How do you force a file to be opened by a particular application?

Question

I have come across a brick wall - I have either missed something important, or maybe it is just something in Applescript not working as it should.
In our school, we have both Preview and Adobe Reader installed on the student computers, which are being managed with Workgroup Manager. There is a particular PDF file which is opened through an Applescript which gives a list of files to choose from (the easiest solution for the situation, which does involve a few variables). Sometimes the file opens in Preview instead of in Adobe Reader. The PDF contains sounds, which Preview doesn't handle, hence the need to open it in Adobe Reader. Rather than going round to many dozens of computers and setting the "open with" info on each computer individually, I thought I would try an Applescript solution. In the example below I have moved the file to the desktop to minimize clutter, but the behavior is the same regardless of where the file is (with the appropriate pathway for its location, of course).
This first script works with no problems, except that it may default to Preview instead of Reader, depending on the setup on the individual computer.
tell application "Finder"
activate
select item "SampleFileName.pdf" of desktop
open selection
end tell
When I consulted the library for Finder, I changed it to the following version which, as far as I can tell, has the correct syntax, etc. However, it comes up with the error message - "Finder got an error: Handler can't handle objects of this class"
tell application "Finder"
activate
select item "SampleFileName.pdf" of desktop
open selection using application "Adobe Reader 7.0.8"
end tell
I have tried the same thing with a generic text file (file name ending in .txt) hoping to use Microsoft Word or Excel, and also using 'open "SampleFileName.pdf" ' directly rather than selecting it first, but I still get the same error message.
Does anyone know what is going on and hopefully know how to fix or work around the problem?

Answer 1

Thank you, Niel.
I tried the script with the file in its final location (to test it out under the actual conditions, as sometimes things on the desktop seem to need different treatment - but that's for another post). It worked like a charm!
I had tried viewing Adobe Reader's dictionary, but it is not scriptable. Your suggestion got around that limitation.
The final script, as per your info, is:
tell application "Adobe Reader 7.0.8"
open file "Users:SampleFile.pdf"
end tell