You can create Page breaks in the output of reporting services, forcing the page break to be between levels of a group for instance instead of at every so many inches of output.
To eliminate (or minimize) page breaks, set a very large page height in the Report Properties dialog. Don't leave it blank or set it to zero, that can lead to performance issues. I commonly set it to 111.
To force page breaks at every group level, go to the Group Properties dialog, and select the Page Breaks screen. Check "Between each instance of a group", and maybe also "Also at the end of a group". You can set page breaks before and/or after tablixes as well.
These manual page breaks that you create in the Group or Tablix Properties cause individual worksheets to be created for each page when exporting to Excel. If you don't want that, you can't fix it in the Group Properties dialog. Instead, select the group and look at the Properties window for the group. Expand the Group section, then expand the PageBreak section. In the Disabled property, select <Expression> and use
=SWITCH(
Globals!RenderFormat.Name = "EXCEL", True,
Globals!RenderFormat.Name = "EXCELOPENXML", True,
True, False)
as the expression. This will disable the page breaks when exporting to excel, but leaves them intact in the web output. And of course you can do the opposite when you want two tablixes to appear on the same page in a web browser, but on separate worksheets in Excel.
For Excel exports, you can set the name of the tabs by populating the PageName property in the Properties window. For a tablix set it to a constant, for a group something like =Fields!GroupVar.Value.