Women keeping silence in the churches

[refreshed]

1Co 14:34  Let your women keep silence in the churches: for it is not permitted unto them to speak; but they are commanded to be under obedience, as also saith the law.

In light of the Scripture above, is it wrong for a woman to give an announcement or a prayer request in a church service?  What about singing a special?  Is there any time when a woman may speak aloud in a church service?