Changing notation in Excel to English

Hi

I have a Danish version of Excel 2003, and am getting crazy because I have to do a lot of calculations with English notation - NOT Danish.

The difference is this:
In English you would write like this: 1,543.34
In Danish it is the opposite: 1.543,34

That means that Excel cannot recognize the English one. How can I change the notation / the language or something that for all inputs to Excel it will be with the English notation???

Help is really appreciated and really needed quickly

thanks in advance

regards
Help-is-needed-quickly