It looks like you are using NetLinx,

OK, this is what I am guessing, it is kind of messed up, if you look at page 3 of the protocol3 xls spreadsheet the following HEX items of the example givin in the .doc never change:

0x080x010x000x000x00P1Checksum

0x080x020x000x000x00P2Checksum

0x080x030x000x000x00P3Checksum


0x040x12commandChecksum

Replace the P1,P2,P3 and command values with the values listed under the headings on Page 1 of the protocol 3 XLS spreadsheet. Now the fun part is to figure the checksum, you can either figure out each one manually or create a subroutine to figure it out in the program you are writing.
formula=CS = ~(08+ 01 + 0 + 0 + 0 + Parameter1,2or3 + 11) +1
which means you add the 8+1+0+0+0+0+11 and subtract that total from $FF and then add 1 which gives you E6. That is the formula they are using for the first three parameter lines, the formula they are using for the command line is: CS=~(04+12+command)+1

The protocol doesn't say anything about the amount of time required between each command so you could try it like the following:
(example contrast command:)
{
send_string dvTV,"$08,$01,$00,$00,$00,$00,$E6"
wait 2 send_string dvTV,"$08,$02,$00,$00,$00,$01,$E4"
wait 4 send_string dvTV,"$08,$03,$00,$00,$00,$5A,$8A"
wait 6 send_string dvTV,"$04,$12,$0B,$DF"
}
AV1 input would be:
{
send_string dvTV,"$08,$01,$00,$00,$00,$00,$E6"
wait 2 send_string dvTV,"$08,$02,$00,$00,$00,$00,$E5"
wait 4 send_string dvTV,"$08,$03,$00,$00,$00,$01,$E3"
wait 6 send_string dvTV,"$04,$12,$0A,$E0"
}