Excel 2007 : Pivot Table Grouping

Hi

I am trying to create a report to show dialling performance across dates, weekdays and hours but want a separate report for each. I have tried to create 2 separate pivot tables for this purpose but when I group one by day the one that is grouped by hour automatically changes to day too! I think they must be linked somehow but can't see how to stop them being linked. It doesn't help that I am using a German version of Excel and am not particularly good at German. Can anybody help?

Thanks

Matt