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.
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.