Parameter Error using Date Format in value

Hi  All,

I am trying to create a parameter for selecting months.  ( Oracle table -  date values are like aug-2014  ) 

The WHERE clause is :   Where To_Date(x.The_Month, 'mm-yyyy')  >  :monthyear 

When I run the report the following error:

Error returned is: ORA-01858: a non-numeric character was found where a numeric was expected..

Here are my parameter settings:

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How can I use the parameter so the WHERE clause will accept the paramter values like "Add_Months(Trunc(Sysdate,'mm')-1,-7)" ?

Thanks in advance.

Collimax

M Collier