Ssrs 2008 using embedded tablixes

In a ssrs 2008, I am going to have 1 main tablix that will have data grouped by student number. Within the main tablix I am going to embed 3 more tablixes. Each tablix will be a report for the selected student. For each of the 3 embedded tablixes, I would like to use 3 different datasets. One dataset for each report.

The problem is in visual studio 2008 for ssrs reports, the designer will only allow me to use one dataset. The designer can see the other datasets.

Thus would you tell me what you would suggest to solve this problem? is there a way to access all 3 datasets? is there some kind of a lookup function? Basically would you tell me what I can do to solve this issue and show me the code and/or point me to a reference that will tell me how to solve my problem?