Does anyone know how to generate a customised unique Opportunity proposal reference?

I am looking to create within SalesForce a customised proposal reference number as an Opportunity field that uses the value from a user defined service line to create a unique reference that is sequential to each service line .... ie

{YY}{MM} (Service_value__c )-{0}

eg 130600-001, 130601-001 etc ...

any help appreciated in solving this one

Fraser - Perth, WA

Does anyone know how to generate a customised unique Opportunity proposal reference?

I am looking to create within SalesForce a customised proposal reference number as an Opportunity field that uses the value from a user defined service line to create a unique reference that is sequential to each service line .... ie

{YY}{MM} (Service_value__c )-{0}

eg 130600-001, 130601-001 etc ...

any help appreciated in solving this one

Fraser - Perth, WA