Applescript my Timbuktu...

I am using the Perform Applescript script in FMP 5. I want the script to open my Timbuktu and navigate to a particular FMP Server. That part works fine. However, after I run the script in FileMaker and Timbuktu comes up, I press "cancel" instead of "OK" then I get an error -27. I know I need an additional line at the end of my applescript that says "If user presses the cancel button then tell application Timbuktu to quit". I just have no idea how to write that in applescript.

My script is pasted below. TIA

tell application "Timbuktu Pro"

activate

open window "New Connection"

end tell

tell application "Finder"

activate

open selection

end tell

tell application "Timbuktu Pro"

activate

make new control session connecting to AppleTalk address {zone:"ADMIN", NBP type:"Timbuktu Host", machine:"MyServerName", network:11111, node:111, socket:111} when rejected let user reenter

end tell

Townsend