As far as mIRC options go, there is not an option to do so. There have been many suggestions for Voice/Video chat being implemented into mIRC on the
Feature Suggestions board. You can also run a
Search on "Voice Chat" - Expand to the 'Feature Suggestions' forum and expand the second drop down list to 'All Posts' for best results.
There may be some scripts which allow you to run a video or voice chat. Check out
mIRCScripts.org and
mIRC.net (They check their submissions for viruses before allowing the public to download them).
G'luck!
Regards,