Converting normal time to Epoch time format using excel

[Colombo]

I'm working on converting some databases. One has entries with normal human readable time format, the other uses the unix epoch time format.

Is there a function or vba code that I can use in excel to convert the normal time format to epoch time?

I've got a thousand or so entries, so it would be nice to find a way to do this on a large scale.

Thanks

Josh