with these inputs, PRICEDISC returns a price for the bond of $82.50.
In Excel, dates are serial numbers. Generally, the best way to enter valid dates is to use cell references, as shown in the example. To enter valid dates directly inside a function, you can use the DATE function. The same formula above using the DATE function, and with other values hardcoded looks like this:
The basis argument controls how days are counted. The PRICEMAT function allows 5 options (0-4) and defaults to zero, which specifies US 30/360 basis. This article on wikipedia provides a detailed explanation of available conventions.