The UDM_GETACCEL message retrieves acceleration information for an up-down control.
UDM_GETACCEL wParam = (WPARAM) cAccels; lParam = (LPARAM) (LPUDACCEL) paAccels;
The return value is the number of accelerator structures retrieved.
If the cAccels parameter is zero and the paAccels parameter is NULL, the return value is the number of accelerators currently set for the control.