Open Explorer (windows) from CRM button

Hi,

how can i open windows explorer for a specific directory from a CRM button in the Web UI ?

The CALL_BROWSER function (which works fine in the SAP GUI) will result in a

500 SAP Internal Server Error

ERROR: Exception condition "FRONTEND_ERROR"  raised. (termination: RABAX_STATE).

How to solve my problem ?

Any suggestions ?

gr

Hans