Usage:
/ISMACRO macro-options
If macro-options matches one or more existing macros, /ismacro returns the number of the last matching macro; otherwise, /ismacro returns 0. Macro-options may include any of the options accepted by /list. If -m is not specified, %{matching} is used.
Example:
/if /!ismacro -b"^X*"%; /then /bind ^X = /foobar%; /endif