You may have learned about sparklines or you want to add a chart to your Tablix. You either copy/paste your working(!!!) chart into the tablix and then you preview and you get:
"The chart 'Chart1' has a detail member with inner members. Detail members can only contain static inner members."
In a Tablix you cannot put dynamic member in a Detail row. You have to put it into a Group header or Group Footer row.
Now you should see something that looks like:
Notice the two rows next to big parenthesis on the left. These are the rows in your group. The top row (where I has the highlighted cell) is the group header row. You can put a chart in any group header row. The bottom row (where the three link icon is) is the details row. If you put your chart in this row, you will get the aforementioned error.
Take care and good luck,