Strange Applescript problem

[tkuypers at pandora.be]

When choosing a folder I get the path in return in the following way:
 Users/ton/Desktop/test Folder

Then I replace all "/" by ":" and add a ":" before "users" so my path to a
specific folder follows AppleScript rules:
 :Users:ton:Desktop:test Folder

Then I complete the path with a file and complete the script:
Tell application "Finder"
 Open alias ":Users:ton:Desktop:test Folder:test.eps"
End tell

When I use this script in the script-editor, it works fine, it automatically
adds the name of my harddisk in front of the path an everything works fine.
When I use this script in Revolution (do myAppleScript as applescript) it
returns an error: Compile error

What am I doing wrong, why doesn't this work???

Warm regards, many thanks in advance,

Ton Kuypers