resize freebsd slice

[Giorgos Tsiapaliokas]

hello,

in my machine i have gentoo and freebsd installed.

i was using gentoo until i installed successfully FBSD,now i want to make my
FBSD slice bigger..

i have 4 slices:

ad0s1->gentoo
ad0s2->linux swap
ad0s3->free space (no type)
ad0s4->FBSD
ad0s4a->/
ad0s4b->FBSD swap
ad0s4c->/home

how can i make my ad0s4a and ad0s4c slices bigger?
P.S.: i want to take space from ad0s3

thanks in advance