I suppose you talk about oowriter and oocalc.
Documents are stored in a compresded (zip). When you unzip an sxw document, content is in content.xml file.
You'll have to use a QDomDocument to get the document structure. Somewhere you'll find your table.
Examine the content.xml from a sample oocalc file. You'll find <table:table-cell> items. Now you can use Qt XML Dom classes to copy from one to the other