DISC calculates and returns the discount rate for a sequrity. @basis is the type of day counting system you want to use:
0 US 30/360
1 actual days/actual days
2 actual days/360
3 actual days/365
4 European 30/360
If @basis is omitted, US 30/360 is applied. If settlement date or maturity date is not valid, DISC returns NUM! error. If @basis < 0 or @basis > 4, DISC returns NUM! error. If settlement date is after maturity date or they are the same, DISC returns NUM! error.