Powershell Cmdlet with 'dynamic' ConfirmImpact attribute set

Class WebSite {
    [string] $Name
    [string] $Category # Can be one of: Production, Test, Development
}

Function CategoryToImpact([string]$Category) {
    Switch ($Category) {
        'Production' {
            [System.Management.Automation.ConfirmImpact]::High
            break
        }
        'Test' {
            [System.Management.Automation.ConfirmImpact]::Medium
            break
        }
        'Development' {
            [System.Management.Automation.ConfirmImpact]::Low
            break
        }
        default {
            [System.Management.Automation.ConfirmImpact]::None
            break
        }
    }
}

Function Remove-WebSite {
    [CmdletBinding(SupportsShouldProcess=$true<#,ConfirmImpact="Depends!"#>)]
    Param(
        [Parameter(Mandatory=$true)]
        [WebSite] $WebSite
    )

    # This doesn't work but I hope it illustrates what I'd *like* to do
    #$PSCmdLet.ConfirmImpact = CategoryToImpact($WebSite.Category)

    if ($PSCmdlet.ShouldProcess("$($WebSite.Category) site $($WebSite.Name)")) {
        Write-Host "$($WebSite.Name) was destroyed"
    }
}

$prod = New-Object WebSite
$prod.Name = 'www.example.com'
$prod.Category = 'Production'
Remove-WebSite $prod

$test = New-Object WebSite
$test.Name = 'test.example.com'
$test.Category = 'Test'
Remove-WebSite $test

$dev = New-Object WebSite
$dev.Name = 'dev.example.com'
$dev.Category = 'Development'
Remove-WebSite $dev