I'm going to assume when you say 'exactly three tables', you actually mean exactly three cells in one Word table. Thereafter I assume you interchangeably use tables to mean cells.

This behaviour is quirky and can be complicated by conversion of formats (Excel to Word) and selection of cells vs selection of rows vs selection of tables.

The method I use is to do two copy paste operations. The first paste requires a conversion from Excel to Word format. I would do this by pasting firstly into a temporary empty document. I then add an extra cell into that table (since copying an ENTIRE table has different behaviour), select the cells I want and copy, then position my cursor in the first cell of the target table where I want to paste (not selecting cells) and do the Paste. If there isn't enough rows below that insertion point, Word automatically adds them.

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Andrew Lockton
Chrysalis Design, Melbourne Australia