I`m assuming you`re talking about Mavic Open Pro rims laced to Ultegra hubs.
My first comment is that if the rim was bent in a crash then trying to correct the situation by adjusting spoke tension would be a big mistabe. The wheel needs to be disassembled and the rim itself straightened (if possible) and the wheel reassembled.
If the rim is beyond repair you`re looking at a new rim. Either way you need to take the wheel apart. Suggest you ask about a loner wheel or bike while the situation is being addressed if riding is that critical and you don`t have a second bike.