How to subset data with some headers in rows?

[#1]

Hi, I have a big data which has headers inside some rows. I wanted to subset the data per header with its value. My data looks something like this:

Header 1	Column 2	Column 3	Column 4
1	1	1	1
1	1	1	1
1	1	1	1
Header 2	Column 2	Column 3	Column 4
2	2	2	2
2	2	2	2
Header 3	Column 2	Column 3	Column 4
3	3	3	3
3	3	3	3
3	3	3	3

I need to subset the data per Header, so I should have Header 2 with 

Header 2	Column 2	Column 3	Column 4
2	2	2	2
2	2	2	2

Header 3

Header 3	Column 2	Column 3	Column 4
3	3	3	3
3	3	3	3
3	3	3	3

I tried creating a Flag column, assign 1 to each header then subset. But the result is incorrect as it subset 1 and blank with Subset 1 with all the headers. This is what I created:

CSV << New Column ("Flag", Numeric);
r = CSV << getRowsWhere( Contains( :Header 1, "Header " ));
Column(CSV, "Flag")[r] = 1;

Please help

[#2]

To create a column with a formula, right click on the column headers to add a new column:

 in the column menu, add a formula

and paste the formula from @jthi 's post.