C# - Globalized Custom Number Formatting - Variable Decimal Points?

I'm trying to alter the existing number formatting in my company's application to make it more readable for international users. This is a stock trading application, so most stock prices come in with numbers precise to 2 decimal points, like so-> 17.23 We could also get ticks in that have precision out to 4 decimal points, so a penny stock might be 0.0341. The original string format that we were using for stocks was "#,##0.00##" Which would give us the format we wanted (essentially trimming '0's). The problem here is the ',' and '.' are forced onto the user, where in many other countries the thousands separator is '.' and the decimal point is ','. Boss man doesn't want to use "N4" for all numbers, even though this would resolve the globalization issue. Is it possible to have a globalized custom string format?

Other options besides writing some middle man code to internationalize numbers formatted the original way or another string.format method?