Reference to worksheet in chart
 

I have a TextBox in chart that refers to a cell in the worksheet the graph is
in. E.g. ='This sheet'!$A$6

In cell $A$6 I have the formula :

If($E$10=$E$100,"L.c. (000)",if($E$10=$E$101,"Dollar(000)","Euro (000)"))

The input in cell $E$10 is validated against the list in $E$100:$E$102
(Local currency, Dollar and Euro respectively).

When the user switches from Euro to Dollar, the value of cell $E$10 becomes
"Dollar (000)", which appears in the chart.

Brilliant! And it works too. I developed this in Excel 2003. When I open the
sheet in 2007, it works too, ............. sometimes.

Sometimes the title in the chart does not change according to the choice of
currency made. The only thing that helps is selecting the TextBox then select
the reference in the FormulaBar as if you will edit it and then press enter.
Then it works again.

Anyone any idea what this could be? And, more important, how I can make it
go away?

Thanks,

Henk