There are lots of ways using the expression language to dynamically respond to changing columns from the node above the expression node but I don't think you'll be able to turn a variable value into a column name on the fly. If you haven't seen reviewed the Expression Language Guide yet, you may find suggestions there.
Need to connect to databases in SAS Viya? SAS’ David Ghan shows you two methods – via SAS/ACCESS LIBNAME and SAS Data Connector SASLIBS – in this video.