Domain Mapping with Networks

i need support
i have WP MU with networks

i wish to redirect sub domain to network
my main network is webvision.co.il
and i have other networks

i want to redircet *.x.com to x.com
and *.y.com to y.com

by now all the sub site redirect to my main web site
webvision.co.il

Please help
and thanks