There isn't one. Events are treated separately so Splunk can't work with values from different events. Exceptions exist for certain functions (range, for instance) in aggregating commands.
Tell us more about the problem you're trying to solve and perhaps we can suggest a solution.
Those two events will have to be combined into a single event so Splunk can "see" both values at the same time and work with them. One problem, however, is there appears to be nothing in common between the events that would tell Splunk they should be joined. Can you elaborate on the use case, please?
If there are only 2 results then this should do the job.
index=foo Tag="Twin_PLC.Twin_PLC.Global.ProdTrend" | rename Value was ProdTrend | appendcols [ index=foo Tag="Board Edger.Edger_PLC.Global.DailyBlkAvg" | rename Value as DailyBlkAvg ] | eval product=ProdTrend * DailyBlkAvg | table ProdTrend DailyBlkAvg product
If there are more than 2 results then Splunk will need to know how to pair them so the calculations are accurate.
I can't see your screen from here so you'll have to write down what results you got and what results you expected to get.