I don't get why TCPnametoIP didn't work for you, i tried it using an array and it worked just fine.
If you're only lookinforward on finding out the ipaddress seens to me you should use StdoutRead instead of running cmd prompt.
There must be easier ways, but heres my way out
#include <Constants.au3>
#include <String.au3>
Global $ctrlarray[3]
$ctrlarray[2] = "sed063" ; Network Computer Name
Func _FindIP ($hostname)
$ping = Run ("Ping " & $hostname & ' -n 1', @SystemDir, @SW_HIDE, $STDOUT_CHILD)
ProcessWaitClose ($ping)
$pingresult = StdoutRead($ping)
$ip = _StringBetween ($pingresult, '[', ']')
Return $ip[0]
EndFunc
$ip = _FindIP ($ctrlarray[2])
MsgBox (0, "IP number", $ip)