Any way to make MUI button react to Enter key?

In MUI is there any simple way I can make an "OK" button react to the Enter key, while still having Enter work with a string gadget as expected? For example, so I can make a MUI equivalent for C:RequestString.

I see that MUIA_Window_InputEvent allows reacting to IDCMP_RAWKEY, but (a) I imagine that Enter will still generate a RawKey event when the string gadget is active, and (b) I have no idea what a "standard commodities.library input description string" is (the unhelpful example is "-repeat f1").