Try & Catch

Hi ,

I would like to use ERROR handling with Try&Catch, that can handle $computername variable, if computer is not found, message comes up: "hey I did not find computer with this name"
to where should I insert try&catch to, in my stuff? a little explanation would be appreciated..

#OSversion attempt:

$ends=""

while ($ends-ne"END") {

$computername=Read-Host"Enter Server's Name "

Get-WmiObject-ClassWin32_OperatingSystem-ComputerName$computername|format-list (

 @{n='ServerName';e={$computername}},

 @{n='WindowsVesrion';e={$_.Caption}},

 @{n='BITVersion';e={$_.osarchitecture}},

 @{n='VersionNumber';e={$_.Version}},

 @{n='ServicePack';e={$_.ServicePackMajorVersion}}

 )

 }

 $ends=read-host"Continue or END "

Thank you in advance