At Debra's suggestion I am posting my message a second time with a bit more
detail :

I have put together a financial budget for 15 years and I now wish to
calculate the incidence of the change in the debt ratio on the ROE (Return on
Equity) of the project.

The debt ratio is a value given in one cell (C47) on Sheet 1 for the first
year and this same value is than copied to the other 14 years to the right

The ROE of the project is calculated in Sheet 2 after going through a series
of formulas in between, which calculate the cash flows of the project over
the 15 years

In Sheet 3 I put the input cell in F5 with the following formula =
Sheet1!C47 to indicate this is the cell I want to change to see the effect on
the ROE

I put the various debt ratios in a column in Sheet 3 (B3:B10) and copy the
formula for the ROE in cell C2 referring to the proper range of cash flows in
sheet 2

Now selecting the cell range B2:C10 and click data table referring to cell
F5 on the same sheet 3 as the column input cell should spill out in C3:C10
the different ROEs under the B3:B10 scenarios ...

For reasons I can't fathom I get all the same values in cell C3:C10 which is
the correct value of the ROE but only if the debt ratio is set at the value
in cell C47 on Sheet 1. If I try to put Sheet1!C47 as the input cell in the
Data Table command, I get an Input cell reference is not valid message
displayed.

What am I doing wrong ??? (Calculation is of course set to Automatic)

Appreciate