Piper said:

The problem: Figure 1

Figure 2

Figure 3

Figure 4

Total (of above four figures)

But Figure 2 MUST BE 10% of the total.

How do I do this in Excel 2003?

Suppose your "figures" 1 through 4 are in A1:A4 and A5 is =SUM(A1:A4).

In A6, put the formula =A5*10%-A2.

Then set up Goal Seek with A6 in Set Cell, zero in To Value, and A2 in By

Changing Cell.

By the way, you can compute A2 directly. You require:

A2 = (A1+A2+A3+A4)*10%

So algebraically:

A2 = A2*10% + (A1+A3+A4)*10%

A2*(1-10%) = (A1+A3+A4)*10%

Note that 1-10% = 90%. So the formula in A2 can be:

=(A1+A3+A4)*10%/90%

or more simply:

=(A1+A3+A4)/9