Andy,
Here's a macro that assigns the activesheet's first embedded chart's title to the filter's first criteria. You could obviously apply the same idea to write the filter criteria into a cell instead of to the chart title.
You can either assign the chart or a button to this macro, so that a single click on the chart or the button updates the chart title from the current filter criteria, or you could use a Chart object Change event to automatically update the title each time the chart changes.
Since you can have multiple filters on a worksheet, I had the macro find the first filter that is On (filtering), but of course you can hardwire it for the particular filter that the chart title is dependent on.
Happy computing.
Damon
Here's the macro:
Sub UpdateChartTitle()
Dim F As String
Dim Fltr As Filter
For Each Fltr In ActiveSheet.AutoFilter.Filters
If Fltr.On Then Exit For
Next Fltr
If Fltr.On Then
F = Fltr.Criteria1
F = Right(F, Len(F) - 1) 'Strip off equal sign at beginning of string
Else
F = "All Criteria"
End If
ActiveSheet.ChartObjects(1).Chart.ChartTitle.Characters.Text = F
End Sub