Looking up data from another model in a joint model

Hi. Really stuck on this.  I have 2 models, one is a CRM system thatrecords client aquistion unti lthey start.  The other is a transaction system that takes over once they start.  My issue is that currently we have to record thestart date in theCRM system by looking up manaully in the transactional system and entering the data. Not suprisingly this is often wrong/out of date.  

The clients have the same account no in both systems. I created a joint model and thoguht it would be trivial to use the CRMaccount no to lookup the start date on the transaction client table and do a comparison.  However depsite creating an inactive relationship bewteen the 2 account numbers netiher calcuate(values(  or Lookupvalue produces any result if I try to add a column to the Client CRM table (which is blank as says (This table uses direct query and cannot be shown). The error is "Client CRM[PP Start Date] cannot be pushed to the remotedata source and canot be used in this scenario"  where Client PP[PP Start Date] is henew column i'm trying to create on the Client CRM table.

Surely there is a way to link the column data from the 2 models that have been joined in a model? It seems to work fine for measures.

Any advice apprecaited

Mike