FM 'FKK_AMOUNT_CHECK_AND_CONVERT' is not triggering Workflow Mail.

Hi All,

I am using the FM 'FKK_AMOUNT_CHECK_AND_CONVERT' for converting the currency, when i am trying the FM in report program i am getting the desired output. But when used inside the method of a class for triggering the Workflow mail. The FM is not allowing the Workflow Mail to trigger, when removing the FM and tried to trigger the Workflow it is working fine.

I need help with this FM, or if any other FM which has to have the import and export Parameters of type CHAR.