String operationName = comboBoxOp.getItem(comboBoxOp.getSelectionIndex());
Variable var2 = getVariableByName(comboBoxVar2.getText());
BSHTypeSupport typeSupport = BSHTypeSupport.getByFormat(var1.getFormat());
Operation operation = Operation.getByName(operationName, typeSupport);
String bsh = operation.generateCode(var1, var2);
bshCodeText.setText(bsh);
} else {
// don't change code
}