MT4 history files

If I understand correctly, data for all timeframes is stored as '.hst' files in one of the MT4 directories.

Does anyone know how to build .hst files for MT4?

I have historical data available from elsewhere that I would like to load into my MT4 - I figure creating/editing a .hst file would be the way to go.

Thanks in advance for any pointers,
O-G

MT4 history files