Merge field for Promotion Code ?

[jols]

With regard to the Promotion Code field in Clients Profile ---> Products/Services.

 

I need to send a customer his promotion code in an email, but I can't find the correct merge field syntax for this one. I've tried a bunch of stuff like:

 

{$service_custom_fields.promoid}

{$service_promoid}

{$service_promocode}

{$client_promoid}

{$client_custom_fields.0}

{$client_custom_fields.1}

{$client_custom_fields.2}

 

But nothing seems to work. Anyone have a hint about this one?

 

Thanks very much.