Discover Private IP dynamically on scaleset

What is the method to get the private IP of a vm in a scaleset at deploy time ?
I've tried the method like in standard vm but it doesn't work
it fails :
`Deployment template validation failed: 'The template reference 'yoyonic' is not valid: could not find template resource or resource copy with this name. Please see http://aka.ms/arm-template-expressions/#reference for usage details.'.`

exemple
"commandToExecute": "[concat('bash myscript.sh ', reference(variables('nicName')).ipConfigurations[0].properties.privateIPAddress)]"