I have a table in Confluence that looks like this:

Note that this table is NOT a Confiforms field. It could be an HTML table, a table returned by a Jira filter macro or from anything that produces a table.
In a form, I define a field -- myfield -- of type Text.
I want to select the value in Col2 based on the Key column and assign the text in the cell to myfield.
I have tried reducing this to a table with a single cell with no headers, thus avoiding the lookup:
I have not been able to find anyway to do this.
As background, I am using a Jira Filter macro and Table Transformer to produce a table of Jira issues. In a Confiforms form, I enter the JIra Key into a field and want to set a text field to the value in Col2 for that Jira Key.
Can you help? Thank you.