Extract a value from a string

[zhshqzyc]

Hello,

Can you advise me what is the best way to get '123456789' from the string

<Log xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://www.nrf-arts.org/IXRetail/namespace/">
<Transaction SourceSystem="1">
<RetailStoreID>999</RetailStoreID>
<RevenueCenterID>0</RevenueCenterID>
<WorkstationID>123456789</WorkstationID>
<RegisterTransactionNumber>122</RegisterTransactionNumber>
</Transaction>
</Log>

Thanks