Column values referencing other column names

I have a column "[EXPRESSIONS]" in my data table that references the names of other columns in the same table. I would like to find a way to create a calculated column that replaces these column names with the value in the corresponding column that is being referenced. Here is an example:

EXPRESSIONS COL1 COL2 COL3 DESIRED COLUMN*
@COL1 @COL3 5 7 1 @5 @1
@COL2 6 4 8 @4
@COL3 @COL2 9 1 7 @7 @1
@COL1 6 2 4 @6

* This is the column I am trying to calculate. The only way I have been able to acheive this is by unpivoting columns to another data table and then inserting them back into my original and matching on that value. I would really like to avoid going through all those steps if this could just be done with a simple formula.

Can anyone help? Thanks!

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