Drag and Drop to App as Service

I have a foreign language dictionary.
Currently if theres a word in Safari I want to look up I drag the word over to the application on the dock. This activates it and shows the translation.

I tried to script this all morning using applescript. Theres only 2 things that needs to be done, create a service and pass the selected text to the service but I can't figure out how to do it because I can't see what the drop command on the application is or how to set its text. I managed to get something going by sending system command v but I had to set the clipboard to do this and I don't want to do that. Should I be doing this with applescript or xcode? Is it possible to interrogate the application to find out what can be set on its interface?