The UDM_SETBASE message sets the radix base for an up-down control. The base value determines whether the buddy window displays numbers in decimal or hexadecimal digits. Hexadecimal numbers are always unsigned, and decimal numbers are signed.
UDM_SETBASE wParam = (WPARAM) nBase; lParam = 0;
The return value is the previous base value. If an invalid base is given, the return value is zero.