Lookup field refresh

Lookup field refresh

Hello,
I have a form which uses lookup fields to gather records from a given (editable) date range. However, I find that when the date range is automatically updated (i.e., I change the month string to "November", which causes a function to execute that updates the  'Report_Start_Date' and 'Report_End_Date' to the first & last of the month), the lookup field doesn't update to show records in the new date range.

However, if the date range is updated manually (i.e., I click on the 'Report_Start_Date' and 'Report_End_Date' fields and select the dates through the pop-up calendar), the lookup field does update. 

Is there a way to force the lookup field to update?

Thanks in advance for your assistance.
Cheers,
Elizabeth

Shared form:  https://creator.zoho.com/climateenergy/freewatt/#Form:FG_HONDA_MONTHLY