// mergeRows.jsx 
 
var curSel = app.selection[0]; 
 
if (curSel.constructor.name == "Cell") { 
  for (var i = 0; i < curSel.cells.length; i++) { 
    var firstCell = curSel.cells[i]; 
    var lastCell = curSel.cells[i+2]; 
    if (lastCell.isValid) {  
      firstCell.merge(lastCell); 
    } 
  } 
}