Dashboard based on Excel Workbooks

I have some data in Excel. I dont wont to change the format of these sheets, because I take out new reports every week. So - I need you to get data from my existing sheets and make a good powerful dashboard from these data.

I need to work "step by step" so we know we have full control. Maybe the best is to price many small individual steps. I will give you one example;

From Finance_Invoice.xlsx
Use the following;
- Navn_Kon
- KategoriNr_Ord
- Text587
- LeveringsDato_Ord
- Netto


From Order_Search.xlsx
Use the following;
- Kategori_Ord
- OrderNr_Ord (link to Text587)
- OrdreDato_Ord
- Netto
- Text502
Do not change the content of the 2 excel worksheets.
1. Count “Tilbud” from “Kategori_ord”, separated into months (based on “OrdreDato_ord”)
o Number of “Tilbud” to this date
o Number of “Tilbud” each month
o Sum of “Netto” each month
o Sum of “Netto” to this date
o Then
o Count “Tilbud” to this date on each of the sellers (Text502”
o Count “Tilbud” each month on each of the sellers
o Sum of “Netto” each month on each of the sellers
o Sum of “Netto” to this date on each of the sellers