title: onMove() or onCursor() or onSelection() trigger in Google Apps Script?
body: <p>I've looked at the <a href="https://developers.google.com/apps-script/guides/triggers/" rel="nofollow noreferrer">documentation for triggers</a>, but couldn't find what I wanted. I essentially want to auto-fill certain spreadsheet cells when the cursor/selection moves to the cell.</p>
  
  <p>For example, say I want any cell in column 'B' that is empty to be filled with the current time when it is highlighted.</p>
  
  <p>How should I be doing that? I see <a href="https://developers.google.com/apps-script/guides/sheets#custom_menus_and_user_interfaces" rel="nofollow noreferrer">Extending Google Sheets</a> refers to <a href="https://developers.google.com/apps-script/uiapp" rel="nofollow noreferrer"><s><code>UIService</code></s></a> and <a href="https://developers.google.com/apps-script/guides/html/" rel="nofollow noreferrer"><code>HtmlService</code></a>, but I didn't find anything about triggers for when current cell changes.</p>