The Excel DISC function calculates the Discount Rate for a bond.
The syntax of the function is:
Where the arguments are as follows:
settlement    The security's settlement date (i.e. the date that the coupon is purchased).  
maturity    The security's maturity date (i.e. the date that the coupon expires).  
pr    The security's price per $100 face value.  
redemption    The security's redemption value per $100 face value.  
[basis]    An optional argument which defines the day count basis to be used in the calculation. Possible values are:

Note that the settlement and maturity dates should be input to the Disc function as either:
Warning: If you attempt to input text representations of dates into Excel functions, the interpretion of these can vary, depending to the date system and date interpretation settings on your computer.
In the following example, the Excel Disc function is used to calculate the discount rate of a coupon purchased on 01Apr2010, with Maturity date 31Mar2015. The price per $100 face value is $95, the Redemption value is $100, and the US (NASD) 30/360 day count basis is used:
A  B  

1  Settlement Date:  01Apr2010 
2  Maturity Date:  31Mar2015 
3  =DISC( B1, B2, 95, 100 ) 
The above function returns the value 0.01.
I.e. the discount rate for a security with the above terms is 1.0%.
Note that, in the above example:
Further examples of the Excel Disc function are provided on the Microsoft Office website.
If you get an error from the Excel Disc function, this is likely to be one of the following:
#NUM!    Occurs if either:

#VALUE!    Occurs if either:
