The Excel Sumsq function returns the sum of squares of a supplied set of values.
The format of the function is:
where the number arguments are numeric values or arrays of values. These can be supplied to the function either directly, as values returned from other formulas, or as references to cells containing numeric values.
If the values supplied to the function are text values, or logical values, these will be handled as follows:
text values: 
 If contained in cells that are referenced by the Sumsq function: Ignored  If supplied directly to the Sumsq function:  If can be interpreted as numeric values: Treated as Numbers  If cannot be recognised as numeric values: Returns the #VALUE! error 
logical values: 
 If contained in cells that are referenced by the Sumsq function: Ignored  If supplied directly to the Sumsq function: Treated as numeric values (TRUE=1, FALSE=0) 
In Excel 2007 and Excel 2010, you can provide up to 255 number arguments to the function, but in Excel 2003, you can only provide up to 30 number arguments.
The spreadsheet below shows examples of the Sumsq function.
The formulas are shown in the spreadsheet on the left and the results are shown in the spreadsheet on the right.
Formulas:

Results:

The above examples show how the arguments to the function can be input as an array, or as multiple values, and how the arguments can be input both directly and as references to cells containing values.
Further information and examples of the Excel Sumsq function can be found on the Microsoft Office website
Although the Sumsq function is able to interpret logical values and text representations of numbers that are supplied directly to the function, as numbers, and will ignore text or logical values that are supplied via a cell reference, you may occasionally get the #VALUE! error returned from the function:
#VALUE!    Occurs if a value supplied directly to the function, cannot be interpreted as a numeric value 