var curDoc = app.documents[0]; 
var allTables = curDoc.stories.everyItem().tables.everyItem().getElements(); 
 
for (var t = 0; t < allTables.length; t++) { 
  var curTable = allTables[t]; 
  var allCells = curTable.cells.everyItem().getElements(); 
  for (var c = allCells.length-1; c >= 0; c--) { 
    var curCell = allCells[c]; 
    if (curCell.appliedCellStyle.name == "mein Zellformat") { 
      curCell.split(HorizontalOrVertical.vertical); 
    } 
  }   
}