The Resolve-Path cmdlet has a -Relative parameter that will return a path relative to the current directory:
Set-Location C:\MyScript
$relativePath = Get-Item Data\Test.txt | Resolve-Path -Relative
The Resolve-Path cmdlet has a -Relative parameter that will return a path relative to the current directory:
Set-Location C:\MyScript
$relativePath = Get-Item Data\Test.txt | Resolve-Path -Relative