I think that the dialog editor should allow to map more SEVERAL defines to the same numeric value.
In a multi dialog application it is very common to have child controls with different 'names' (like BTN_OPEN_IMAGE in dialog_x, BTN_OPEN_WAVE in dialog_y) that map to the same value:
#define BTN_OPEN_IMAGE 1000
#define BTN_OPEN_WAVE 1000
Gil.