Alternative to LOOKUPVALUE

I have got this to work, but I really don't like how I have done it, and was wondering if there was a better way?

I have two tables:

1. TankID: contains the unique tank ID plus related information on the tank
2. FuelLevels: contains three columns-  TankID, Date/Time, FuelLevel

I have a new calculated column in tankID, whos job it is to get the latest fuel level for that tank from FuelLevels.

I have a relationship set up on TankID, (one to many, single way filtering)

calculated column is: 

Logic: searching the FuelLevels table:

• search column: date/time. Find the latest date/time, and search for this value

I dont really like this part, it seems messy, but it works.

• Search tankID column in FuelLevels, search for the current TankID.

I really dont like this, as it seems superflous. (this should be done by relationships?)

Can someone tell me how to do this better!!

Many thanks

*edit*

I want to use something like this: