I got a refresh button working by adding this function to the code:

function increment()
{
  SpreadsheetApp.getActiveSheet().getRange('L1').setValue(SpreadsheetApp.getActiveSheet().getRange('L1').getValue()+1);
}

Then drawing a button like this: http://stackoverflow.com/a/6966272
and attaching the increment script to it.

No luck yet on getting auto-refresh to work.