Since version <insert the version number here>, multiple action urls can be set for a service.
Syntax is :
define service {
service_description name of the service
[...]
action_url URL1,ICON1,ALT1|URL2,ICON2,ALT2|URL3,ICON3,ALT3
}
* URLx are the url you want to use
* ICONx are the images you want to display the link as. It can be either a local file, relative to the folder webui/plugins/eltdetail/htdocs/ or an url.
* ALTx are the alternative texts you want to display when the ICONx file is missing, or not set.