does the current Citrix environment run via the F5? if so then you could apply a redirect iRule or Local Traffic Policy on the virtual server to redict them to the new URL.
if it doesn't run on the BIG-IP yet you would have to create a VIP there point DNS to it and create the redirect iRule or Local Traffic Policy.
this is quite a usual request so there are many examples here, look for something and see if it works, if it doesn't post what you got and someone will be able to help.
[EDIT] why the title of your question btw? it doesn't really cover the topic of it, might want to change that.