"Not as long as we have his daughter."
can i say "Nicht solange wir haben seine Tochter" or is it compulsory to use verb at the end while using "solange"
no, that word order doesn't work. Give this a read: http://german.about.com/library/weekly/aa032700a.htm
I guess your question should read the other way round: in this case, it is 'solange'. You write 'so lange' if 'so' and 'lange' are understood as separate entities. Duden gives a few examples of when to use which spelling: http://www.duden.de/rechtschreibung/solang_inzwischen_waehrenddessen
Is "Nicht weil wir seine Tochter haben." a good translation as well? It was not accepted as a correct answer.