How to parameterize azure agent.name in azure pipeline?

I am trying to parameterize the agent.name in azure pipeline. The objective is to give the user the option to deploy the code in the desired machine. So I have created a pool with a few machines in it and parameterize the agent.name

Code

parameters
- name: machinename
  displayName: machinename
  type: string
  values:
  - 10.72.1.123
  - 10.72.1.124

pool:
  name: PoolA
  demands:
    - agent.name -equals ${{ parameters.machinename}}

Error : When trying to run the above code , I get the below error.

A template expression is not allowed in this context

Please help in resolving this issue.

You may try to use this workaround:

trigger: none

pool:
  name: Default
  demands:
  - agent.name -equals $(machinename)

jobs:
- job:
  displayName: 'Job 1'
  steps:
  - task: Bash@3
    inputs:
      targetType: 'inline' 
      script: |
        echo "$(machinename)"

then please define pipeline variable (on editing pipeline):

Make this variable available of overwriting:

and then n running pipeline:

You will not get dropdown list, but this is the only way to overcome this issue.