You don't have to use ACSX, you can perfectly use Text/XML transformation with your repeater, so your dont have to chanage your macro and it will work.
It possible with ACSX but conditional statements are kind of awkward:
<%# IfTrue(CMS.DocumentEngine.DocumentContext.CurrentDocument.GetValue("showPhone"),"555-555-5555")%>
There is a couple posts on this topic: post1, post2, but I would just use Text/XML.