extend/shrink LVM between different volume groups

Bear with me on this one, since I'm pretty new to LVM.

I have a server with about 5 LVM's on them. They consist of 5PV, using their own VG's and their own corresponding LV's. My issue is, I'm needing to know if it is possible to shrink one of the LV's a bit, and give that extra space to a different LV and expand the other LV. Here's a glimpse of my configuration:

LV That I want to shrink by 30GB
PV /dev/cciss/c0d1p4 VG vg4 lvm2 [76.88 GB / 0 free]

LV That I want to expand by 30GB from the previous LV
PV /dev/cciss/c0d1p2 VG vg2 lvm2 [46.57 GB / 0 free]

/dev/cciss/c0d1p4 is a mount point called /u03 and /dev/cciss/c0d1p2 is a mount point called /backup. They are on two different volume groups. I'll show the output of pvdisplay, vgdisplay, and lvdisplay for these LVMs:

pvdisplay Output

  --- Physical volume ---
  PV Name               /dev/cciss/c0d1p4
  VG Name               vg4
  PV Size               76.89 GB / not usable 3.25 MB
  Allocatable           yes (but full)
  PE Size (KByte)       4096
  Total PE              19682
  Free PE               0
  Allocated PE          19682
  PV UUID               aMo010-TaQn-ehsK-29R9-aFat-HGK4-vwMPMA

  --- Physical volume ---
  PV Name               /dev/cciss/c0d1p2
  VG Name               vg2
  PV Size               46.57 GB / not usable 1008.00 KB
  Allocatable           yes (but full)
  PE Size (KByte)       4096
  Total PE              11922
  Free PE               0
  Allocated PE          11922
  PV UUID               ML2gdx-wkwW-C2tZ-rX5b-hVhQ-xZhq-C1cIFx

vgdisplay Output

  --- Volume group ---
  VG Name               vg4
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               76.88 GB
  PE Size               4.00 MB
  Total PE              19682
  Alloc PE / Size       19682 / 76.88 GB
  Free  PE / Size       0 / 0   
  VG UUID               wbVABu-LR3G-1c5f-qfz8-3eLD-vTEq-1FFrfo

  --- Volume group ---
  VG Name               vg2
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               46.57 GB
  PE Size               4.00 MB
  Total PE              11922
  Alloc PE / Size       11922 / 46.57 GB
  Free  PE / Size       0 / 0   
  VG UUID               aVO4SZ-RVFU-FJfq-QTKi-NBDZ-rWiB-keb41m

lvdisplay Output

  --- Logical volume ---
  LV Name                /dev/vg4/lv_u03
  VG Name                vg4
  LV UUID                edVjf2-wPmY-wRUL-QwIT-PJ1Q-m128-rppA3a
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                76.88 GB
  Current LE             19682
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:3

  --- Logical volume ---
  LV Name                /dev/vg2/lv_backup
  VG Name                vg2
  LV UUID                n2PaAn-S8jl-yQdu-HVyR-pZcI-X9S9-GgeQ4K
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                46.57 GB
  Current LE             11922
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:5

Any help would be appreciated.