The Standard Normal Distribution is a simplified version of the Normal Distribution Function which arises when the mean of the distribution is 0 and the standard deviation is 1.
Therefore, the Excel Norm.S.Inv function is the same as the Norm.Inv function with the mean and standard_dev arguments set to 0 and 1 respectively.
The Standard Normal Cumulative Distribution function and the Inverse of this function are shown in the graphs below:
The Excel NORM.S.INV function calculates the inverse of the Standard Normal Cumulative Distribution Function for a supplied probability value.
The Norm.S.Inv function is new in Excel 2010 and so is not available in earlier versions of Excel. However, the function is simply an updated version of the Normsinv function, which is available in earlier versions of Excel.
The syntax of the function is:
Where the supplied probability argument is the probability value (between 0 and 1), at which you want to calculate the inverse of the standard normal cumulative distribution function.
Note that Excel uses an iterative method to calculate the Norm.S.Inv function and seeks to find a result, z, such that:
In the spreadsheet below, the Excel Norm.S.Inv Function is used to calculate the inverse of the Standard Normal Cumulative Distribution Function for 3 different probability values.
Formulas:
 Results:

Further information and examples of the Excel Norm.S.Inv function are provided on the Microsoft Office website.
If you get an error from your Excel Norm.S.Inv function this is likely to be one of the following:
#NUM!    Occurs if the supplied probability argument is ≤ 0 or ≥ 1. 
#VALUE!    Occurs if the supplied probability argument is nonnumeric. 