After (a lot of) trying and testing I got the following to work:
on convertToCIN(obj, VI)
try
set objectfile to (obj as alias)
set VIfile to (VI as alias)
tell application "lvsbutil.app"
Convert objectfile Saving as CIN For PPC In VI VIfile
end tell
VIfile
on error errMsg number errNum
display dialog "Failure: " & errMsg & " <" & errNum & "> " & ¬
" in converting " & (obj as string) & ¬
" to " & (VI as string)
return false
end try
end convertToCIN