Google Spreadsheet Data Validation by Reference

refvalidation.gs

/* Google Spreadsheet Data Validation by Reference
   Author: Henrique Bastos <henrique@bastos.net>
   License: MIT
*/

function onEdit(e) {
  var rule = e.range.getDataValidation();
  
  if (rule == null) {
    return;
  }
  
  var value = e.range.getCell(1,1).getValue();

  var criteria = rule.getCriteriaType();
  var validationRange = rule.getCriteriaValues()[0];

  var i = findInRange(value, validationRange.getValues());
  var ref =  validationRange.getCell(1,1).offset(i, 0).getA1Notation();
  e.range.getCell(1,1).setFormula("=" + ref);
}

function findInRange(value, tableValues){ 
  for (var i = 0; i < tableValues.length; i++) {
    if(tableValues[i][0] == value) {
      return i;
    }
  }
  return -1;
}