Enter the concentrations of the standards and their instrument 
readings (e.g. intensity, absorbance, etc) into the blue table 
on the left. Leave the rest of the table blank. You must have 
at least two points on the calibration curve (3 points for the 
quadratic and 4 for the cubic calibraiton), including the 
blank (zero concentration standard). If you have multiple 
instrument readings for one standard, it's better to enter 
each as a separate standard with the same concentration, rather 
than entering the average. The spreadsheet automatically gives 
more weight to standards that have more than one reading.

Enter the instrument readings (e.g. intensity, absorbance, etc) 
of the unknowns into the yellow column on the right. You can 
have any number of unknowns up to 20. (If you have multiple 
instrument readings for one unknown, it's better to enter each 
as a separate unknown, rather than averaging them, so you can 
see how much variation in calculated concentration is produced 
by the variation in instrument reading). 

The concentrations of the unknowns are automatically calculated 
and displayed column K. If you edit the calibration curve, by 
deleting, changing, or adding more calibration standards, the 
concentrations are automatically recalculated.

For "CalibrationLinear" and "CalibrationQuadraticB", column L 
estimates the standard deviation of each concentration caused 
by uncertainty in the calibration curve, as calculated by the 
algebraic proparagion-of error rules and by the bootstrap method, 
respectively. These estimates will only be useful if there are 
at least 5 or 6 standards (but the more the better). Column M is 
the relative percent standard deviation.

You can remove any point from the curve fit by deleting the 
corresponding X and Y values in the table. To delete a value; 
right-click on the cell and click "Delete Contents" or "Clear 
Contents". The spreadsheet automatically re-calculates and 
the graph re-draws; if it does not, press F9 to recalculate.  

Don't type anything into columns K, L, or M; they contain 
important formulas.