once my friend said about already a game in excel, so how is it possible?

Answer 1

Gamges for Microsoft Excel can be written using VBA (Visual Basic for Applications). See Wikipeida article for details:
http://en.wikipedia.org/wiki/Visual_Basic_for_Applications

You can find some VBA games here:
http://www.geocities.co.jp/SiliconValley-Cupertino/5678/

Answer 2

It's not technically a game, but there is a flight sim style thing in Excel 97.

Excel - Excel 97 Flight to Credits
1. On a new Worksheet, Press F5
2. Type X97:L97 and hit enter
3. Press the tab key
4. Hold Ctrl-Shift
5. Click on the Chart Wizard toolbar button
6. Use mouse to fly around - Right button forward/ Left button reverse
N.B. You need to have direct draw installed for this egg. If you don't, you'll get the message: "This would be much more interesting if you were running with DirectDraw. But you're not, so this will have to suffice", and the credits will appear.