Default column selection

Hi

Here, to focus on the issue, I have developed a column chart which is based on combo box selection(Unit 1 and Unit 2). The default selection is given as 1 for the column chart. Data Insertion is given as Position and mapped to series 1 and series 2.

I select the first column and the position is shown as 1,1 (series 1, series2)

Still in the same combo box selection, I select second product (column 2, series2). the position changes to 2,2 (series 1, series2)

Then I change the combo box selection to Unit 2.

the position still is 2,2. Whereas I want the default selection to be 1,1. Suggestions please. Does Source data component help in capturing the index. Am running out of ideas and clues.

Sruthi