If you want to skip the barometric part, leave off that paramater, and the "standard" pressure of 29.921" Hg. will be used.
Now for SI units as well:
elevm = meters
barom = millibars (hPa)
so, as above, you'd do something like,
If you'd like to include these calculators on your site, simply make up an HTML form with inputs for elevation and (optionally) barometric pressure.
The key lines in your form will be either or both of these:
Full Boiling Point Calculator