Combining data of two crosstabs

Migrateduser

<p>Hi guys,<br><br>
what seems extremely easy in Excel is not in Birt I guess. I have two datasets based on two different db tables. For both datasets I created each a crosstab that gives me accumulated results for each month. I want now create a third table or crosstab that shows me computed results from the two before mentioned tables.<br><br>
Example:<br><br>
First crosstab shows me number of sales per platform and month.<br><br>
The second crosstab shows me the number of returned item also per platform and month<br><br>
in a third table I now want to use these numbers to show the quote of returned items (returned items / soled items * 100) also per platform and month.<br><br>
I already tried using a global persistent variable that stores the numbers from the first crosstab and tried to use it in the second to build the quote. This seems already to work, but how do I now build up the third table and fill it with the numbers from the GPV?<br><br>
Or maybe I'm thinking much too complicated and there is a much easier solution?<br><br>
I appreciate every hint :-)<br><br>
Thanks and best regards<br><br>
Marc</p>