With the following Google Apps Script you can grab the LIBOR value and added it to a new sheet. Goto the script editor:  
![enter image description here][1]  

and add this script:  

    function myCustomCalculation() {
      //set active spreadsheet
      var ss = SpreadsheetApp.getActiveSpreadsheet();
      
      // flush the spreadsheet before using it  
      SpreadsheetApp.flush();
    
      // get both the sheets 
      var sh0 = ss.getSheets()[0], sh1 = ss.getSheets()[1];
      
      // get cell value from sheet[0]
      var cell = sh0.getRange("D2").getValues()[0];
      
      // add libor value to other sheet  
      sh1.appendRow([new Date(), cell]);
    }

The clue to the story is to create a time based trigger:  
![enter image description here][2]  

and set the trigger to execute at 5-6 pm:  
![enter image description here][3]

See the example file I´ve created: [LIBOR][4]. I've added an extra menu item, so that you can execute the script this way.


  [1]: https://i.sstatic.net/znyRM.png
  [2]: https://i.sstatic.net/5pOM4.png
  [3]: https://i.sstatic.net/ZMwYl.png
  [4]: https://docs.google.com/spreadsheet/ccc?key=0ApDwwZxW-IBcdGZCMWR4TUx5dUhqaWtMejd4VzVSU1E