Powershell Script assistance required -

i'm piping file's contents select-object , creating 2 properties each name, computername , fileexists, latter value result of test-path

get-content c:\users\admin\documents\scripts\serverlist.txt | `    select-object @{name='computername';expression={$_}},@{name='folderexist';expression={ test-path "\\$_\c$\data\repository"}}, @{name='size';expression={$_.sum}} 

i want return size of folder if exists on each server. how ?

tried adding

@{name='size';expression={$_.sum}} 

to select-object not return value

i think looking for

  get-content c:\users\admin\documents\scripts\serverlist.txt | select-object @{name='computername';expression={$_}},@{name='folderexist';expression={ test-path "\\$_\c$\data\repository"}}, @{name='size';expression={ "{0:n2}" -f ((gci -path "\\$_\c$\data\repository" -recurse | measure-object -property length -sum).sum /1mb) + " mb" }}