Let PowerShell analyze and decide the data type. It internally uses a 'Variant' for this.
And generally it does a good job...
param($x)
$iTunes = New-Object -ComObject iTunes.Application
if ($iTunes.playerstate -eq 1)
{
$iTunes.PlayerPosition = $iTunes.PlayerPosition + $x
}
Or if you need to pass multiple parameters:
param($x1, $x2)
$iTunes = New-Object -ComObject iTunes.Application
if ($iTunes.playerstate -eq 1)
{
$iTunes.PlayerPosition = $iTunes.PlayerPosition + $x1
$iTunes.<AnyProperty> = $x2
}