output a particular string

Hi experts,

I have many files it contains like below.

GET:SUB:MSI,7601;
RESP:0:SISDN,72030067:MSI,7601:T11,1:T21;
GET:SUB:MSI,7602;
RESP:0:SISDN,72030068:MSI,7602:T11,1:T21;
GET:SUB:MSI,7603;
Resp:1000;
GET:SUB:MSI,7604;
Resp:1000;
GET:SUB:MSI,7605;
RESP:0:SISDN,72030069:MSI,7605:T11,1:T21;

How can i make the output as- In fact, i need to fetch the strings that comes after MSI:7602;
And if Resp:[^0] then "none"
7601
7602
none
none
7605

//purple

awk -F: '{ if (substr($4,1,3)=="MSI") { print substr($4,5) } else { if ($1=="Resp" && $2 > 0) { print "none" } } }' input_file

great..and many thanks.

just want to know what is the logic behind. a little explanation...

-F: --> This declares ":" as the field separator
MSI comes in the 4th word.
If first 3 char of 4th word is "MSI"
print 5th char onwards of 4th word
else
If first word is "Resp" and second word is > 0
print "none"
end if
end if

okay..I applogies I missed the point to make u understand.

in fact, i have to only manupulate on- "RESP:0:SISDN,72030067:MSI,7601:T11,1:T21;"

i need to only fetch the MSI from RESP:0.

if Resp:1000 i.e Resp not equal to zero then print None.