Idk what you want exactly but :
1 - You need need a special version of mame that manage the Hight score, idk if you have the good one.
2 - this mame version generate *.hi file that contain the hightscore.
3 - the application HiToText.exe can convert the *.hi to text file
4 - you can use this file where you want, but idk if you just want to see the hightscore in mame or in mGalaxy ?
Not sure for all, I don't use this feature, I m using standard Mame.