Hi,
Thanks for the question! We can help you with this issue, but I’m going to need a little more information first.
Which browser is in use while accessing Excel Web apps?
Were the Excel functions in English language prior to the issue?
If you are using Internet explorer then try to reset and check if it helps;
http://support.microsoft.com/kb/923737
Disclaimer: The Reset Internet Explorer Settings feature might reset security settings or privacy settings that you added to the list of Trusted Sites. The Reset Internet Explorer Settings feature might also reset parental control settings. We recommend
that you note these sites before you use the Reset Internet Explorer Settings feature.
Also check if the issue persists when you use a diffrent browser.
Check regional and language settings are set correctly.
The United States-International keyboard layout is selected.
For more information refer:- http://support.microsoft.com/kb/306560
I hope the above steps helps. If you need any further assistance reply and we will be glad to assist you.
Thanks