title: Excel VBA requiring file extension for workbook reference in some systems
body: <p>I have a simple excel VBA that is referring multiple files and copying information across to a master before processing. While building this on my own system a workbook reference (working perfectly fine) was written as:</p>
  
  <pre><code>Workbooks("key").Sheets("Sheet1").Range("A1:X57").Copy
  </code></pre>
  
  <p>Here key is a .xlsx file</p>
  
  <p>While using this in another system this does not work and it explicitly requires the file extension in every call. </p>
  
  <pre><code>Workbooks("key.xlsx").Sheets("Sheet1").Range("A1:X57").Copy
  </code></pre>
  
  <p><strong>It would not be extremely difficult for me to make this change although I wanted to understand why this is happening and can I define an Option (guessing!) that would not require me to do so?</strong></p>
  
  <p><strong>Why is there difference in behaviour across systems while running the same script?</strong></p>
  
  <p>Any help would be much appreciated. For me this seems like VBA having a mind of its own.</p>