It's impossible to protect some file for some time. Intrinsically, the file doesn't have any property that will allow it to know whether it's January, 1st, 2010 or 30-Feb-2050 (if February will have 30 days in 2050).
What "could" know the time is the program opening it. In your case, Excel. But a program itself doesn't know about time either. It would need to know the specific time from some source, verify it the time was reached or not, and act accordingly.
That leads to some problems:
1 - It must be impossible to change the program, or that time restriction would be circumvented. Doing some research about tamper-resistant software will show you that it's hard to do it: DVD protection, Blu-ray protection, and many other kinds of data protection, have failed. Perhaps digital tokens, used to store private-keys, are the only ones that haven't being defeated yet, but I'm not sure.
2 - Your program must get the time from a reliable source. How you assure that your source is reliable or not is another problem. Atomic clock? Adjusted by who ?
3 - The communication between your program and the clock must also be secure.
4 - Once open, you have to assure that it will be impossible to "save" the file content to any other archive. And that includes taking pictures or memorizing the information and typing it again in another excel worksheet.