change maxlength of an existing column in a list via powershell?

Question

I have the following code to create a list, however I need to increase via powershell the maxlength of one column

$spWeb = Get-SPWeb -Identity http://ost-dev1.ciredev1.local
 $listTemplate = [Microsoft.SharePoint.SPListTemplateType]::GenericList 
 $spListCollection = $spWeb.Lists 
 $spListCollection.Add("ExternalSites","External Sites",$listTemplate)
 $spList = $spWeb.GetList("/Lists/ExternalSites")
 $spFieldType = [Microsoft.SharePoint.SPFieldType]::Text 
 $spList.Fields.Add("ExtSiteUrl",$spFieldType,$false)
 #$spList.Fields["ExtSiteUrl"].Title = "External Site Url"
 $spList.Fields.Add("ExtSiteDescription",$spFieldType,$false)
 #$spList.Fields["ExtSiteDescription"].Title = "External Site Description"

 $spList.Update()

Answer 1

Do you try to use something like this?

$spField = $spList.Fields["FieldName"]
$spTextField = $spField -as [Microsoft.SharePoint.SPFieldText]
$spTextField.MaxLength = 128
$spTextField.Update()