Dependency Tree

Using a dependency tree is the technique that Excel uses to minimise the re-calculation required in a workbook.
When a workbook is recalculated it only needs to update the following:
0) Formulas or Names that have changed
1) Formulas containing volatile functions
2) Formulas dependent on changed, volatile formulas, cells or names

Excel works out the dependencies by looking at the cells referred to by each formula and the argument list of each function.
Dependency trees are immediately updated whenever a formula is entered or changed
To force the dependency tree to be rebuilt and to re-calculate all formulas press (Ctrl + Alt + Shift + F9)

Are there any Excel Dependency Limits ?

In Excel 2003 there were two limitations:
1) The number of different areas in a sheet that could have dependencies is limited to 65,536
2) The number of cells that can depend on a single area is limited to 8,000.
If either of these are exceeded the full calculation is performed instead of a recalculation.