This really isnt a 'Script Request' forum, you might want to see
this post for an example limiting script, or, checkout a few scripting depots (i.e.
mIRCscripts.org,
ScriptsDB.org, or a few others listed on this
LINKS page of this website.) to download an existing one.. failing that you might want to have a look at the helpfile and at least attempt to code one.
Eamonn.