Powershell: Load Exchange Tools

I am creating an universal Powershell script for Exchange 2007/2010 installations.  

I want to have a function which checks if the Exchange SnapIn is already loaded.  Depending on the installation, it only should try to load the Exchange 2007 or Exchange 2010 SnapIn.

That's what I have at the moment which is creating a Warning as it either only finds one or the other Snapin.

function LoadExchangeTools {
	if (-not (Get-pssnapin | ? {$_.name -like 'Microsoft.Exchange'})) {
		Add-PSSnapin Microsoft.Exchange.Management.PowerShell.e2010
		Add-PSSnapin Microsoft.Exchange.Management.PowerShell.Admin
	}
}

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I want a function which checks which Exchange version is installed and then only tries to load the appropriate Snapin.

Thanks!!