you can try using the union option to combine two data sources.
Please find the link for your reference.
Yes, I've read that already but I can't work out how to combine different excel files.
If they are all in the same excel worksheet I have no problems doing UNION etc, but when they are in different ones I can't.
If you have two different excel sheet you can use the cross join which is being implemented from tableau 10.
it would be great if you can share your data and we can work on it to get the desired result.
You've to use data blending here. For blending your data source should have some common fields so that you can join. Its similar to joining keys in database which we called blending keys here. I guess you've already identified your common columns in your data source. Now connect both the sources in tableau. Then go to data menu> edit relationship. There you've to map your fields. Follow the below link for step by step walk though.
Let us know If this help.