how to edit proxy.pac file

Hi... I have a proxy.pac file that gets applied through group policy so that if users from our office use the internet it goes through our proxy server, but if they are outside our network than the connection is direct. I want to modify this file so that it applies for all our other offices throughout the country. The file currently is as follows:

function FindProxyForURL(url,host)
{
if(isInNet(myIpAddress(),"10.21.1.0","255.255.255.0"))
return "PROXY 10.21.1.32:8080";
else
return "DIRECT";
}

I tried to modify it myself, but it doesn't work, as I don't really know the write syntax or what language it even is. But from my attempt, you should be able to see what I'm trying to achieve:

function FindProxyForURL(url,host)
{
if(isInNet(myIpAddress(),"10.21.1.0","255.255.255.0"))
return "PROXY 10.21.1.32:8080";
or
if(isInNet(myIpAddress(),"10.21.2.0","255.255.255.0"))
return "PROXY 10.21.1.32:8080";
or
if(isInNet(myIpAddress(),"10.21.3.0","255.255.255.0"))
return "PROXY 10.21.1.32:8080";
or
if(isInNet(myIpAddress(),"10.21.4.0","255.255.255.0"))
return "PROXY 10.21.1.32:8080";
or
if(isInNet(myIpAddress(),"10.21.5.0","255.255.255.0"))
return "PROXY 10.21.1.32:8080";
or
if(isInNet(myIpAddress(),"10.21.6.0","255.255.255.0"))
return "PROXY 10.21.1.32:8080";
or
if(isInNet(myIpAddress(),"10.21.9.0","255.255.255.0"))
return "PROXY 10.21.1.32:8080";
else
return "DIRECT";
}

any assistance would be appreciated.