ireport table component merge cells

For example,now I want to merge table header,column 1-4.Steps as below:

 

Firstly,I choose the columns under table hearder menu,and right click the mouse and choose the

 

option "Group selected columns",then you will find another column named "Empty Group Header"

 

appear under table header,and the columns you selected combine to a new item,"Columns 1-4" right

 

click the "Empty Group Header" column and choose "Add cell",you will find the cells merged,then go to

 

the columns1-4 item,and delete all columns under the item.