A pseudo environment variable named errorlevel stores the exit code:

echo Exit Code is %errorlevel%

Also, the if command has a special syntax:

if errorlevel

See if /? for details.

Example

@echo off
my_nify_exe.exe
if errorlevel 1 (
   echo Failure Reason Given is %errorlevel%
   exit /b %errorlevel%
)

Warning: If you set an environment variable name errorlevel, %errorlevel% will return that value and not the exit code. Use (set errorlevel=) to clear the environment variable, allowing access to the true value of errorlevel via the %errorlevel% environment variable.

Deleting the shortcut from the "C:\Users\username\AppData\Roaming\Microsoft\Internet Explorer\Quick Launch\User Pinned\TaskBar" leaves the icon on the taskbar but in an unusable state and clicking it pops up an error that it doesn't exist and asks if you want to remove it. I'm guessing that this is what you want to avoid.

There doesn't seem to be a simple way to do this, but there's a Module available in the TechNet Script Center that does the trick:

Pin and unpin applications from the taskbar and Start-menu

###########################################################################" 
 #  
 # 
 # NAME: PinnedApplications.psm1 
 #  
 # AUTHOR: Jan Egil Ring, Crayon 
 # 
 # DATE  : 06.08.2010  
 #  
 # COMMENT: Module with the ability to pin and unpin programs from the taskbar and the Start-menu in Windows 7 and Windows Server 2008 R2. 
 # 
 # This module are based on the Add-PinnedApplication script created by Ragnar Harper and Kristian Svantorp: 
 # http://blogs.technet.com/kristian/archive/2009/04/24/nytt-script-pin-to-taskbar.aspx 
 # http://blog.crayon.no/blogs/ragnar/archive/2009/04/17/pin-applications-to-windows-7-taskbar.aspx 
 # 
 # Johan Akerstrom`s blog: http://cosmoskey.blogspot.com 
 # 
 # For more information, see the following blog post: 
 # http://blog.crayon.no/blogs/janegil/archive/2010/02/26/pin-and-unpin-applications-from-the-taskbar-and-start-menu-using-windows-powershell.aspx 
 # 
 # VERSION HISTORY: 
 # 1.0 17.04.2009 - Initial release by Ragnar Harper and Kristian Svantorp 
 # 1.1 26.02.2010 - Update by Jan Egil Ring. Added the capability to unpin applications. 
 # 1.2 06.08.2010 - Update by Johan Akerstrom. Added full MUI support. 
 #  
 ###########################################################################" 


function Set-PinnedApplication 
{ 
<#  
.SYNOPSIS  
This function are used to pin and unpin programs from the taskbar and Start-menu in Windows 7 and Windows Server 2008 R2 
.DESCRIPTION  
The function have to parameteres which are mandatory: 
Action: PinToTaskbar, PinToStartMenu, UnPinFromTaskbar, UnPinFromStartMenu 
FilePath: The path to the program to perform the action on 
.EXAMPLE 
Set-PinnedApplication -Action PinToTaskbar -FilePath "C:\WINDOWS\system32\notepad.exe" 
.EXAMPLE 
Set-PinnedApplication -Action UnPinFromTaskbar -FilePath "C:\WINDOWS\system32\notepad.exe" 
.EXAMPLE 
Set-PinnedApplication -Action PinToStartMenu -FilePath "C:\WINDOWS\system32\notepad.exe" 
.EXAMPLE 
Set-PinnedApplication -Action UnPinFromStartMenu -FilePath "C:\WINDOWS\system32\notepad.exe" 
#>  
       [CmdletBinding()] 
       param( 
      [Parameter(Mandatory=$true)][string]$Action,  
      [Parameter(Mandatory=$true)][string]$FilePath 
       ) 
       if(-not (test-path $FilePath)) {  
           throw "FilePath does not exist."   
    } 

       function InvokeVerb { 
           param([string]$FilePath,$verb) 
        $verb = $verb.Replace("&","") 
        $path= split-path $FilePath 
        $shell=new-object -com "Shell.Application"  
        $folder=$shell.Namespace($path)    
        $item = $folder.Parsename((split-path $FilePath -leaf)) 
        $itemVerb = $item.Verbs() | ? {$_.Name.Replace("&","") -eq $verb} 
        if($itemVerb -eq $null){ 
            throw "Verb $verb not found."             
        } else { 
            $itemVerb.DoIt() 
        } 

       } 
    function GetVerb { 
        param([int]$verbId) 
        try { 
            $t = [type]"CosmosKey.Util.MuiHelper" 
        } catch { 
            $def = [Text.StringBuilder]"" 
            [void]$def.AppendLine('[DllImport("user32.dll")]') 
            [void]$def.AppendLine('public static extern int LoadString(IntPtr h,uint id, System.Text.StringBuilder sb,int maxBuffer);') 
            [void]$def.AppendLine('[DllImport("kernel32.dll")]') 
            [void]$def.AppendLine('public static extern IntPtr LoadLibrary(string s);') 
            add-type -MemberDefinition $def.ToString() -name MuiHelper -namespace CosmosKey.Util             
        } 
        if($global:CosmosKey_Utils_MuiHelper_Shell32 -eq $null){         
            $global:CosmosKey_Utils_MuiHelper_Shell32 = [CosmosKey.Util.MuiHelper]::LoadLibrary("shell32.dll") 
        } 
        $maxVerbLength=255 
        $verbBuilder = new-object Text.StringBuilder "",$maxVerbLength 
        [void][CosmosKey.Util.MuiHelper]::LoadString($CosmosKey_Utils_MuiHelper_Shell32,$verbId,$verbBuilder,$maxVerbLength) 
        return $verbBuilder.ToString() 
    } 

    $verbs = @{  
        "PintoStartMenu"=5381 
        "UnpinfromStartMenu"=5382 
        "PintoTaskbar"=5386 
        "UnpinfromTaskbar"=5387 
    } 

    if($verbs.$Action -eq $null){ 
           Throw "Action $action not supported`nSupported actions are:`n`tPintoStartMenu`n`tUnpinfromStartMenu`n`tPintoTaskbar`n`tUnpinfromTaskbar" 
    } 
    InvokeVerb -FilePath $FilePath -Verb $(GetVerb -VerbId $verbs.$action) 
} 

Export-ModuleMember Set-PinnedApplication