Do you mean u want to send a channel message, but one that shows only to +v nicks? If so I dont think you can.

If you mean you want to limit a persoanl message to NickX to only send if he is a +v then use $nick(#channel,NickX,v) to see if hes +v

;/vmsg nick message
;belliesup if your not in a channel
alias vmsg { if ($nick(#,$$1,v)) { msg $1 $$2- } }

or

;vmsg channel nick message
;channel is the channel to check if the nick is +v on
alias vmsg ( if ($nick($1,$$2,v)) { msg $2 $$3- } }