I am using ANTLR 3

I am trying to custom the exception message raised from Praser.

Expression which I am using :-

```
2+*3

```

Error message recived from ANTLR is :

```
no viable alternative at input '*' line 1:3

```

I want to custom this exception message to 

```
 Invalid Expression Term line 1:3

```

I tried to override `GetErrorMessage(RecognitionException e, string[] tokenNames)` method of parser but not able to figure out how to customize this description.
Similar to these I've to customize other exception message also.

Can anyone provide me some initial guidance how to proceed with this issue.

I am using c# 4.0