How to write the regex to extract a field from XML data if the field is not completely XML?

Hi I have a field which I would like to extract a field from the XML being displayed. The only problem is the field is not completely XML. I am not allowed to post an example, but basically I want to extract something that looks like: Event xml 0005530001214811TransferStarted And I would like to grab **TransferStarted** in between the two tags <bos:implementationName> and </bos:implementationName>. I have worked with regex in the past, but am still not confident. Any help would be much appreciated and Happy New Year!