BM_SETCHECK does not check a radio button

I am calling this method:

Helpers.WinApi.SendMessage(nextControl, Helpers.WinApi.BM_SETCHECK, Helpers.WinApi.BST_CHECKED, new StringBuilder());

Where: BM_SETCHECK constant is 0x00F1 and BST_CHECKED is 1.

This message is totally ignored.

How can I do it? Thanks Jaime