Simple iRule For DNS Intercept on Big IP DNS

Thanks for the quick response. What you have replied with is what I actually did, as it seemed to make sense to me; however, it's still not working. I have a LTM DNS VIP which load balancing to 2 Windows DNS servers. I've applied a DNS profile to the VIP and applied the iRule to the VIP, but if I do a NSLOOKUP for 'abc.domain.private' against the VIP address, which is where I'd expect the query to get intercepted by the iRule it just comes back "*** [10.222.42.4] can't find abc.domain.private: Non-existent domain".

I also have GTM DNS listeners configured too, but I'm pointing the NSLOOKUP to the LTM DNS VIP. I've also tried implementing Youssef's GTM example, at a GTM level, but I get a syntax error with that.

I was hoping to try and solve this myself, but it looks like time to reach out to our F5 SE. Thanks for attempting to help me. Much appreciated.