Get field value from most recent record

Hi, I am looking to automate a sequential numbering system, so each new item within an app will have it's own unique four-digit number.  How can podio look at the most recently created record and get the field value for reference number, then create a workflow to automatically update the calculation field in the record I just created to be the number of the previous record + 1 ?

That way podio takes care of attributing a new unique, sequential number to each record which is created.   I will be importing old records to the app from a spreadsheet, so won't be starting from 1, but need to look at the most recently created record. 

Thanks

Ben