I use LiveSplit (http://livesplit.github.io/) with the SourceSplit (https://github.com/fatalis/SourceSplit/releases) component.

To enable for the MOD version, set your "Game Name" to "Black Mesa" in "Edit Splits", then make sure to hit Activate for auto splitting. Doesn't look like it works for the Steam version though :(... You might want to submit an issue (https://github.com/fatalis/SourceSplit/issues) to request game compatibility.

http://www.moddb.com/mods/black-mesa/downloads download "Black Mesa Part 1.zip" & "Black Mesa Part 2.zip". Sorry for late reply lol...

I love these games so much :D

gibe demo