Default value if item is not supported

[Inc0]

Hello,

I'm using Zabbix 2.0.4; I have many items whose value is calculated as a sum of items from other hosts:

BW_IN:last("Server1:net.if.in[eth0,bytes]")+last("Server1:net.if.in[eth1,bytes]")+last("Server2:net.if.in[eth0,bytes]"+last("Server3:net.if.in[eth0,bytes]")

This value is used to plot a graph and everything works fine if all items return a value but if for some reasons (for example if an host goes offline) an item doesn't return a value, the graph isn't plotted anymore until until the item starts collecting data again.

My question is: is there a way to make an item return a default value (let say 0) if he can't retrive data?

Thanks

[Inc0]

Anyone? Do I need to specify more infomations?

Please help me, I can't figure out how to solve this problem

[albort]

I really want to help you, but I am also new to here, and I have not so many experience at this field. I believe that, a expert will help you to solve this problem!