Load Record To Form Depending On Value In Combo Box

Hey,
I have 2 combo boxes. The first one gives a lis of Prefix letters for railcars. The second uses the value of the 1st and finds railcars that start with the same letters.

finally got the 2nd combo box to list the prefix and number of a railcar based on the 1st combo box and also got it to clear as each run-through starts.

Now that the user can select a number (ex. dfcv1234 as the railcar), I need to find the record with the prefix dfcv and the car number 1234 and load the record to the form for view and editing.

So far, I know it needs to be the after update event and have a select statement that finds the [key], [prefix], [car_number] that matches the value selected on the form but how do I use the key to make the record show on the form?

Thanks,
slh