Help with iRule for smtp server

Hi,

 

I'm trying to configure a iRule, but I haven't succes. I've two ISP connected to Link Controller, and I want to configure an internal smtp server to balance these ISP's in function of least connections, how I can configure the LC so that when you choose the ISP1 modify the package with the SNAT pool x.x.x.x and when choose the other ISP put another snat y.y.y.y? I don't want to choose automap. I tried this but didn't work:

 

 

when LB_SELECTED {

 

if { [IP::addr [LB::server addr] equals 10.0.0.254] } {

 

snat 1.1.1.1

 

}

 

elseif { [IP::addr [LB::server addr] equals 10.0.1.254] } {

 

snat 2.2.2.2

 

}

 

 

Thanks