How to get week-over-week % in pivot table for dissimilar data

Hi:

I am trying to build an excel report which can get me week over week data.
Data tab1, current week: It has columns -- manager name, employee name, vendor, and a group code
Data tab2, previous week: It has same columns as above.

The number of rows will potentially be different every week in both the above data tabs.

The catch is that every week each manager can have a different employee, vendor, group code combination. So there's no way I can do a look up and get the metrics as one row item.

I want to aggregate the data as pivot table--
Aggregated by Manager name; and having columns manager name, employee name, metric 1, metric 2, Week-over-Week metric %

How can I pivot the data to get the week-over-week data aggregated at Manager Name (regardless who his/her employees were/are)?

title updated