explained locale difference.

Tusky · Tusky · commit d760dd9e6130 · 2015-07-21T07:58:31.000+02:00
diff --git a/docs/tutorials/Addin01.md b/docs/tutorials/Addin01.md
@@ -36,7 +36,7 @@ Next write your user-defined function in Python. In the previous step ExcelPytho
 
 * Switch back to Excel and click 'Import Python UDFs' in the ExcelPython tab to pick up the changes made to `Book1.py`.
 
-* Enter the formula `=DoubleSum(1; 2)` into a cell and you should get the correct result:
+* Enter the formula `=DoubleSum(1, 2)` or `=DoubleSum(1; 2)` depending on your Excel version's locale into a cell and you should get the correct result:
 
     ![image](https://cloud.githubusercontent.com/assets/5197585/3917596/e5365b3c-238e-11e4-8bce-0d97caceca2e.png)
     
@@ -46,4 +46,11 @@ Next write your user-defined function in Python. In the previous step ExcelPytho
     ?DoubleSum(1, 2)
     ```
 
+    or
+    
+    ```
+    ?DoubleSum(1; 2)
+    ```
+
+
 To continue move onto the [next tutorial](./Addin02.md).
