Scripting to MultiSelect Linked.. only works when ...

[VentureOff]

I am struggling to find the formula that I need.

I am trying to calculate the total guide cost for a trip.  I have a multiselect field for the guides that will be on the trip, then in the guide table, I have their rate per hour of guiding.  So on the main table, I have a lookup field that displays the rates for each guide.  I need to now multiply each rate by the 8 hours and then by the total number of days they are out,  and add them together.  

https://airtable.com/shrDEDCYEnQAlksAF

[Alexey_Gusev]

Hi,
Change lookup field to rollup, SUM(values). Multiply it by 8 and total number of days.