Save file in Adobe After Effects automatically


I have a file open in after effects and i want save it, in a specific folder with an applescript, y had tried some like this

tell application "Adobe After Effects CS5"
		save document in "MACINTOSH HD:Users:grafisme:Desktop:file" as ".aep"
end tell

but dont work, what are im doing wrong?, if i use system event to control virtually the mouse clicks i arrive to the save dialog, but default route is the desktop and i dont know how change this route to save the file in a specific folder (this folder change every day, so i must use a variable to locate it)