Aligning line chart with column chart (4 categories)

Hi All,

I am trying to plot a line chart over a column chart (4 categories). The
columns on the primary y-axis, while the lines on the secondary y-axis. The
problem is that the line charts starting points are always at the middle of
the data series but not properly aligned with the columns. I want to shift
them and align them with the column charts. Here is the data.

2011 2011 2012 2012
Volume % of sector Volume % Sector
Company 1 150 7% 310 11%
Company 2 170 5% 320 12%
Company 3 160 4% 330 13%

If you plot them in columns, you will see 4 groups on the X-axis: Volume
2020, % Sector 2020, Volume 2030, % Sector.

But I want it to be showing only 2 groups (representing years)on the X-axis:
2020 and 2030, and in each year, there are 3 columns (for volume on the
primary y-axis), and over them there is the line chart (on the secondary
y-axis):

one blue line starting from Company 1 column at 7% on the secondary y-axis
in 2011, extending to Company 1 blue column in 2012 at 11%. Another red line
for company 2 following the same idea. And a green line for the last green
column for company 3.

I look forward to your feedback.

Thanks in advance