Use the Permission interface FileAppend property to determine if a group or client has permissions to append files in a folder, and to allow or deny appending permission.
Signature:
HRESULT FileAppend([out, retval] VARIANT_BOOL *pVal);
HRESULT FileAppend([in] VARIANT_BOOL newVal);
True = Allowed
False = Prohibited
Refer to Permission Interface Properties for an illustration of how this and other Permission properties can be accessed in the Administrator interface.