Creating dynamic calculated column

I have a table with a “Service” column. I then have an unknown number of columns called “Service0”, “Service0amt”, “Service1”, “Service1amt”, etc.

I need to create a new column called “directamt” that will pick up the “Service0amt” if the “Service” value matches to the “Service0” value. The “Service” value will only ever match up to one of the new “Service_0” columns.