Finally, a Grammar Check for German! (I'll ace that comp & con class now!)
by Michael Shaughnessy - German Program at Washington & Jefferson College
Before you rejoice and run off to sell that grammar reference book you spent $132 on, take a close look at the Grammar Checker provided by MSWord.
With automatic language detection on, and the proper files installed, the computer will underline grammar errors in green.
For an (admittedly bad) example, let's take a look at these pearls of sentences.

To access the grammar information, you can either RIGHT-CLICK the word or start the grammar program under TOOLS.
For the first example, the ending on mein- is feminine. The computer recognizes this and tells you...

I am of the opinion that if you can understand "Kongruenz, Überprüfen Sie die Flexionsformen der Ausdrücke Bruder und Meine," then you should also be able to know that the correct form is simply "mein".
Basically, it says. This appears to be wrong.
Let's look at the next item.

Ok, the explanation is convoluted, but this time the program has a suggestion! And.. it is correct! This thing is great!
Let's do another!

So the correct ending is dem? That was easy!
Actually, no. Sorry. The correct ending is not dem, but das, and the program missed some other easy targets in the sentences.
Basically, don't trust this snake-oil salesman. Ignore it completely, pay attention to the grammar explanations in your classes and find a way to learn it so that you can understand it. It may be 300 years before a grammar program is perfected and we want to go to a German speaking country ASAP!
Not convinced, try the new Korrektor Plus! It also misses many common grammar errors! Also try learning German in a cultural context with CAPL.