QUOTE(ThegreatQ @ Feb 4 2008, 04:17 PM)

Yes but when you open the racemenu with "showracemenu" then you can manually turn the player into every race and the opposite sex, no matter what clothes or armour you wear. Why doesn´t that work with one single skript?
The race menu isn't script based, it's hard coded. You can't initiate any of those changes without having to force that menu to come up. And that menu only applies to the player character, not any NPCs.
As far as NPCs go, it seems like you can initate a sexchange, but the NPC cannot be in the currently loaded cell, and needs to be respawned after that change is made. Since this is a companion, both of those are things which probably won't work too well since scripting on the companion will only run while they're in the loaded cell, and respawning the companion will usually clear any changes, like inventory, or added packages. They however will use the body meshes and sounds of the other gender, but their face, skin and hair will look the same. If the NPC is in the loaded cell the game will crash, If they havn't been refreshed by the game (either through respawning or saving then reloading), the game will crash as soon as they are within the loaded cell.