Hello @Bob Umlas,
Apologies for the delay in my response. Sometimes, features are slowly rolled out to a certain percentage of Office Insiders. That was the case for the LAMBDA function but it should now be available to 100% of Windows Beta channel Insiders.
Cheers,
Evan
Office Insider Community Manager
Become an Office Insider and gaining exclusive access to new features and help shape the future of Office. Join Now: Windows | Mac | iOS | Android