Is it possible to create a table in the header of Excel 2010?
No you can't do that I'm afraid.
However, you can simulate it to a certain degree. You have three areas to work with (left middle right) and you can have multiple lines though you may need to adjust the margins to fit.
Unfortunately, you will not be able to have borders.
If you need more than this. I would recommend not using the headers but instead simply have a table at the top of your spreadsheet that you make repeat on each page. That way you can have pretty much anything. If you need a table that doesn't match the table layout of the remainder of the spreadsheet, just do the header table in PowerPoint or Word and copy/paste it into place.
There is a pretty good solution.
What I did do was creating the rows I want in the header at the top of the cells. Print screen and adjust the image and save it somewhere on your desktop. Then go your header and add the image you just made (inside the first header). Because this is not a perfect solution - but very close - you need to adjust the column width of some of the columns.
Now you can delete the rows you'd made in the first place at the top of the cells. And as you can see the image appears in your header on every page.