diff --git a/gui/models/data_storage.py b/gui/models/data_storage.py
index 8adfa26..9517f92 100644
--- a/gui/models/data_storage.py
+++ b/gui/models/data_storage.py
@@ -86,6 +86,7 @@ class DataStorage(QObject):
     }
     _EXPR_ALIAS_TYPES = {
         'cv': 'Candidate (CV)',
+        'aux': 'Auxiliary',
         'cst': 'Constraint function',
         'obj': 'Objective function (J)'
     }
@@ -1491,7 +1492,8 @@ def check_simulation_setup(self):
         # get expressions validity
         expr_df = self.expression_table_data
         expr_valid_check = expr_df['Expression'].apply(
-            lambda x: is_expression_valid(x, aliases['Alias'].tolist())
+            lambda x: is_expression_valid(x, aliases['Alias'].tolist() + expr_df['Alias'].tolist()
+            )
         )
 
         is_name_not_duplicated = pd.concat(
@@ -1644,6 +1646,10 @@ def evaluate_expr_data(self, sampled_data: pd.DataFrame,
                 expr_row_values[expr['Alias']] = expr_to_parse.evaluate(
                     row_val_dict)
 
+                row_val_dict.update(
+                    {expr['Alias']: expr_row_values[expr['Alias']]}
+                )
+
             # append values to expr_df
             expr_df = expr_df.append(expr_row_values, ignore_index=True)
 
diff --git a/gui/models/sampling.py b/gui/models/sampling.py
index 1984195..b893781 100644
--- a/gui/models/sampling.py
+++ b/gui/models/sampling.py
@@ -442,6 +442,7 @@ def model_function(self, x):
             expr_to_parse = parser.parse(expr['Expression'])
             var_list = expr_to_parse.variables()
             expr_values[expr['Alias']] = expr_to_parse.evaluate(results)
+            results.update(expr_values)
 
         # separate constraints values
         con_aliases = expr_data.loc[