Tools > Solver amounts to a more elaborate form of Goal Seek. The difference is that the Solver deals with equations with multiple unknown variables. It is specifically designed to minimize or maximize the result according to a set of rules that you define.
Each of these rules sets up whether an argument in the formula should be greater than, lesser than, or equal to the figure you enter. If you want the argument to remain unchanged, you enter a rule that the cell that contains it should be equal to its current entry. For arguments that you would like to change, you need to add two rules to define a range of possible values: the limiting conditions. For example, you can set the constraint that one of the variables or cells must not be bigger than another variable, or not bigger than a given value. You can also define the constraint that one or more variables must be integers (values without decimals), or binary values (where only 0 and 1 are allowed).
Once you have finished setting up the rules, you can adjust the argument and the results by clicking the Solve button.
The Solver dialog
 The default solver supports only linear equations. For nonlinear programming requirements, try the EuroOffice Solver or Sun’s Solver for Nonlinear Programming [Beta]. Both are available from the OpenOffice.org extensions repository. (For more about extensions, see Chapter 14 (Setting up and Customizing Calc.)
