title: Combine lookup with arrayformula
body: <p>Edit: This Spreadsheet explains the situation: <a href="https://docs.google.com/spreadsheets/d/1oQdHvWOb19evsJeeyCzc52_aPPt47LfEqe81YyNYRV0/edit?usp=sharing" rel="nofollow noreferrer">Lookup and Arrayformula</a></p>
  
  <p>I have a select list in my configuration Sheet (B1). Here a user can select Data Set 1 or 2.</p>
  
  <p>Now in column <code>E</code> I want to display the Values for each URL accordant to the config. </p>
  
  <p><code>={"Value from chosen Dataset";
  ARRAYFORMULA(
  LOOKUP(B2,{"Data Set 1","Data Set 2"},
  {IFERROR(VLOOKUP($D2:$D1000,G1:H1000,2,FALSE),""),
  IFERROR(VLOOKUP($D2:$D1000,J1:K1000,2,FALSE),"")}))}</code></p>
  
  <p>As you can see there is an error which says my usage of LOOKUP is somewhat faulty. I feel like I run into issues because I want to LOOKUP one single field but then perform an ARRAYFORMULA based on that single cell.</p>
  
  <p>Any ideas to resolve this? Feel free to edit the spreadsheet.</p>