what you might want to do (if not already) is simply bind the chart to the query through the report wizard. if you've already done that, just change the query source if you need to.
the great thing about graphs and charts is that they automatically produce crosstab queries. e.g. - they can group a dataset on two fields, and read it like a simple SELECT query.
If you are simply using years, there's a bunch of ways. is your chart using the datefield series (x-axis) with the FORMAT() function? The first thing I would do is put a criteria line in the query (if the chart is based on the query) to grab the year from the combo:
Code:
WHERE year([DateField]) = forms!formName!ComboName
or...if the combo has actual dates in it, maybe:
Code:
WHERE year([DateField]) = year(forms!formName!ComboName)
Again, it really depends heavily on what format the actual date is in. Charts are smart enough to group on the date as long as it is in a format that is recognized by Access. That includes dates that have been manually formatted with the FORMAT() function.