How to do computations in parameter Mapping

[a_nat]

Can I concat 2 process variables and  create a task parameter.

Assume that I  have 2 process varaibles named CustomerID and IdProofName and now if I have to create a new task varaible named "RecordId" which is a concat of CustomerID, string " gave " and  IdProofName, can I do this in the Parameter Mapping section  of human task.

Viz.., if

CustomerId = 123,

IdProofName = Passport,

I want  the result as

RecordId = 123 gave Passport

Kindly note that I don't want to store it in process variable and also don't want to use On Entry . If there are other options, I would love to know about it.

[a_nat]

Also when I provide value to the "Content" field of the task, the "Parameter Mapping" section is totally ignored, why is that?