Differentiate code in script depending on called from another script or shell

I'm trying to differentiate code in script, A, when script, A, is called from another script,B, versus when it runs on it's own.

Script A

$callingScript = $MyInvocation.MyCommand.Source | Split-Path -Leaf
if($callingScript -eq "$($MyInvocation.MyCommand.Name)"){
    # Script is run from Shell
}else{
    # Skript is called from script B.ps1
}

Script B

(...)
& "$($PSScriptRoot)\A.ps1" 

The result is always $callingScript is A.ps1 and Name is also A. Any ideas how to accomplish this?