You can use HyperlinkAddress and HyperlinkSubAddress to help you out.
You can use a command button to trigger the event. Just add a command button to a form. Then open its Properties and type a path to your target db in Hyperlink Address and the macro name in Hyperlink SubAddress.
You can click the browse button (...) on the right side of the Hyperlink Address to find the target db and click that of the Hyperlink SubAddress to get the macro name.
What do you want to run the macro for anyhow? Using the hyperlink will open another instance of Access and may don't want this to happen. Tell me what does the macro do and maybe I will find a workaround for it.