Merging leads based on a custom field

[Anonymous]

Hi,

I am looking to merge leads in Marketo automatically that share the same value for a custom field (in this case the user id assigned by a company which owns many websites and uses this id across all).

Is it possible to set a custom field as the key lead differentiator, and then merge any leads that share this value?

Any help would be appreciated!

Kind regards,

Luis