This might help you navigate to a folder once the save dialog is raised:
set the clipboard to "/path/to/your/folder"
tell application "System Events" to tell process "SketchUp" -- I'm guessing on SketchUp name
keystroke "G" using {command down, shift down}
delay 1
keystroke "v" using {command down}
delay 1
keystroke return
delay 1
keystroke return
delay 1
end tell