A spreadsheet formula is an equation that performs a calculation on the numbers, functions and values of one or more cells. A formula is associated with a cell or a cell range. It is accessed using the Range.Formula property.
A formula is a string expression that begins with an equal (=) sign. A formula can contain the constants, operators, cell references, calls to functions, and names.
Consider the following formula, which calculates the mass of a sphere.
=4/3*PI()*(A2^3)*Density

“4” and “3” are numeric constants. Although they are written as integers, the division operator (/) interprets them as being real numbers, i.e., 4.0 and 3.0. As a result, the calculation produces a precise result that is not rounded to an integer.

“/” is the division operator.

“PI()” results in a call to the PI function, which returns the value of p.

“A2” is a cell reference, which returns the value within that specific cell.

“3” is a numeric constant.

“^” is the caret operator, which raises the left operand to the power of the right operand.

Parentheses are used for grouping and changing the operator precedence.

“*” is the asterisk (*) operator, which performs multiplication.

The Density is a defined name within the worksheet that can represent a cell range, a function or a constant.
The formula is calculated from left to right, according to the operator precedence. To change the order of calculation you can enclose a portion of the formula in parentheses.
To recalculate all formulas in a workbook, call the IWorkbook.Calculate method. The DocumentSettings.Calculation property provides access to calculation options. Calculation results are placed in the Range.Value property of corresponding cells. See the Calculation topic for more information.
You can also calculate a formula and leave the document unchanged by using the IWorkbook.Evaluate method.
The FormulaEngine is an object that provides the capability to calculate and parse worksheet formulas. It includes a builtin formula parser, as well as the flexibility to evaluate formulas in any range of any worksheet. See the Formula Engine topic for more information.