Calling a module name from a dynamic variable

[Franks Andy (IT Technical Architecture Manager)]

Hi all,
  Freeradius 3.1 from git.

Just wanted to know if I can do this :

Update control {
  Tmp-String-0 := "mymodule"
}

"%{control:Tmp-String-0}" {
  Fail =1
}

Hopefully it's obvious - I want to prepare a variable and call a matching module name from the variable, in this case mymodule.
It doesn't work at the moment as the string isn't evaluated - it just says:

Failed to find "%{control:Tmp-String-0}" as a module or policy.

If I can't, I can't no worries, I would just stop me searching if I knew.

Thanks
Andy