Any active macro can be triggered using the kmtrigger: scheme with a URL like this:
kmtrigger://macro=MacroName&value=Value
Note that a macro must be active (that is, it must be enabled, and the macro group that contains it must be enabled and active) in order for the macro to be triggered by any means including via URL.
You can pass a parameter to the macro by adding the value field to the URL. The parameter is available to the macro as the %TriggerValue% text token (v7.0+).