Numbers 09 - Date and not either change

[Sillynsky]

Hello together,

first sorry for my english, but my last english lession is far away (i´m german).

I have a problem with Apple Numbers. I have follow function:

(German) =WENN(A1="fertig";HEUTE();"")
(in english) =if(A1="ready";TODAY();"")

The problem is "TODAY" changed by openn the document. I wont a fix date. Have anybody a idear?

Thanks
Silly