Customising Host name for Discovery Rules?

I understand that there are features within foreman that allows some customisation of hostnames
eg. Myhost-<%=@host.ip.to_s()%> that allows customising based on facts retrieved from the host.

I would like to know if this feature is extended to taking on values from Foreman itself?

For example, i would like to have my hostname to take on some custom values that tracks the number of hosts within a hostgroup

e.g. Myhost-HG1-<% "no of host in hostgroup %>

Expected outcome:

I am looking to have my host provisioned with running number



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