Reassign based on Out of Office

We have a client that uses workflow and they are wanting to have the workflow assign it to a backup AP Processor if the primary is out of the office. The problem is not every primary processor has a backup processor. I have created a substitution rule and list, with the users that actually have backup users.

In the workflow manager I know I can assign it directly, using the substitution rule, but if a user doesn't have a backup then it should stay in that users task list. Is this possible?

Thanks

what if you try assigning the backup to a variable and if there is no backup then have a condition check to see if its blank and if its blank assign an elevated user

I guess that is the way I will have to do it, with as many steps that the client has this may take a bit. Thanks for helping!

EDIT: One question though, how is the system going to know if someone is out of the office?

We ended up using a web service to read the Out of Office status from the database then populate a field with true or false. I then had conditions that check for the true or false and then assign the correct backup user.