First of all, you should understand that this is not a problem at all: as you don't need to support the tables in an Excel sheet and only need the export, you can place any number of tables on the single sheet: each table have a finite size, so you can put, say, two table in different location of the sheet. If you, say, shift second table on the right of the first one, you can even grow them later, as the tables have fixed number of rows.
For creation of the Excel files, you can either use Microsoft Word interop (it requires Excel to be installed) or Open XML SDK:
http://en.wikipedia.org/wiki/Open_XML[
^].
As you did not share information on your programming language, platform and other detail, that's all.
—SA