You can do this in your query ...

SUM(t1.fieldtosum) OVER (PARTITION BY t1.groupfield) fieldsummaryvalue

Check out the workaround described here:

http://connect.microsoft.com/SQLServer/feedback/details/527455/error-in-report-designer-innermost-group-does-not-have-a-grouping-cell

You have a couple options for doing this in SSRS 2008, both involving Placeholders.

Option 1:

Type in "Name: " and set the TextBox FontWeight property to Bold.

To the right of "Name:...