The Complementary Error Function is equal to 1  ERF (i.e. 1  Error Function), and is given by the equation :
The Excel ERFC function calculates the Complementary Error Function, integrated between a supplied lower limit and infinity.
The format of the function is:
where x is the lower limit of the integral.
The Erfc function was improved in Excel 2010 in that it can now accept negative function arguments.
In Excel 2007 or earlier, if you input a negative value for the argument, x, the function would return an error. However, in Excel 2010, the function algorithm has been improved, so that it can now calculate the function for both positive and negative x values.
The spreadsheet below shows examples of the Excel Erfc function being used to calculate the Complementary Error Function integral for different lower limits.
Formulas:

Results:

Further examples of the Excel Erfc function can be found on the Microsoft Office website.
If you get an error from the Excel Erfc function this is likely to be one of the following :
#NUM!    Occurs in Excel 2007 or earlier, if the supplied value of x is negative 
#VALUE!    Occurs the supplied x is nonnumeric 
#NAME?   
Occurs when Analysis ToolPak addin is not enabled in your Excel. + Show How to Do This in Excel 2003: 