One simple way would be to embedd Survey B in survey A itself using an iframe.

You could add an ED to surveyB, lets say surveyAResponseID and in your iframe append query strings in the URL of survey B to keep track of this.

This way you can link all completions of surveyB which have come through surveyA and don’t need track who all return, as they’ll still be inside survey A.

Thanks @ahmedA . Much appreciated . Will try now and check the UI. Conscious we may hit a legal bump ‘integrating’ clients study (survey into ours this way - not sure they will go for it. But let’s see. If they don’t do you know if it’s possible to route out and back as per my original workflow??  

Do you have any control over the client survey? If no, then your router becomes quite complex, though not impossible.

Client survey is used for more than this project so reluctant to change anything in the UI that side if can avoid. Tested the iframe option. Nice elegant solution...thanks for the idea. Only concern is risk some progress Survey A before finishing B (as buttons sit under each other). Might need to accept some risk here. Would still like to explore ‘route out and back’ option if you think possible as this way we can control progression loop 100%. Should be able to add ED to client survey without too much trouble. Thanks for any further thoughts!    

Maybe show it in a modal. That would solve the next button issue and also help with the legal concern.

For the route out option, the simplest way is to give them a hyperlink... Ask them to complete and come back. I'm sorry, but I'll need to see the surveys to provide more details on this option. 

For the simple iframe, you could hide the next button on survey A and send a message from Survey B to tell survey A that survey B is finished. This will require JS. 

@Daxo,

To route out and back you need to use Save & Continue and Survey B must redirect back to original Survey A url. You need to use ajax, an external database to track respondents, and a couple of web scripts.

Thanks both @ahmedA and @TomG 

So got a green light from client with iframe. Changed progress button styles on both to differentiate and added instructions to clarify. Modal looks great and will do next time, but am approved with current so keen to move forward. The route out and back model looks more challenging. Thanks both for exploring all the same. Super advice from you guys...much appreciated :) Daxo