Finally! A question I can answer before Alfred Eller sees it!
(Alfred is the intelligent, warm, helpful and devilishly handsome mainstay of GenForums FOW page.)http://genforum.genealogy.com/fo/
Click on File -> GEDCOM -> Export
When the box comes up, it will have "All Individuals" checked. Check the other one, "Selected Individuals".
FOW will let you select all the ancestors of (someone), all the descendants of (someone), all the people who served in the Civil War, or all the left-handed blondes, for that matter. Its selection box is great. You can specify how many generations, too.
Play around with it. You can try the selection logic on a custom report to see who will come up if, for instance, you want all the ancestors of a specific person.
"Ancestors of" and "Descendants of" give you sub-selections. Both have the "Entire ancestral line" option. You may find it easier to alter your data slightly, make the GEDCOM, then fix what you unlinked. For instance, if you were sending everyone you had collected on your husband's side to his cousin, you could unlink yourself as a spouse from him, select him and "entire ancestral line", export the GEDCOM, and send it off. Afterwards you'd enter your marriage relationship again.
The only problem my FOW (8.0) has is in spouses. If I want to send a GEDCOM of six generations of ancestors with the spouses, I have to either use "Ancestors of" again and again on the GGG Grandparents, or add the spouses individually.