add a second workbook to Excel

$erroractionpreference = “SilentlyContinue” 
$a = New-Object -comobject Excel.Application 
$a.visible = $True
$b = $a.Workbooks.Add() 
$c = $b.Worksheets.Item(1)
$c.Cells.Item(1,1) = “Computer Name” 
$c.Cells.Item(1,2) = “OS Version” 
$c.Cells.Item(1,3) = “IP vLan” 
$c.Cells.Item(1,4) = “Description” 
$c.Cells.Item(1,5) = “Model” 
$d = $c.UsedRange 
$d.Interior.ColorIndex = 37   
$d.Font.ColorIndex = 1       
$d.Font.Bold = $True 
$d.EntireColumn.AutoFit()
$intRow = 2

The above code works but how do I make it create a second workbook (SHEET2)?   I've played around with this code but I've yet to have it create a sheet2.