rdlc how to keep together specified rows

Hi,

I have to "keep together" 2 rows (tablerow) one with title of image and second with image.

Bacis my report have grouping formula like this "<GroupExpression>=RowNumber(Nothing)</GroupExpression>"

I try to add custom property to my items

<CustomProperties><CustomProperty><Name>grouping</Name><Value>1</Value></CustomProperty></CustomProperties>

and use it in <GroupExpression>, but i dont know how.