No. Merging requires 2 or more columns.

From MSDN Reporting Services Books Online:

Merging Cells

Multiple contiguous cells within a table can be combined into a single cell.
This is known as a column span or a cell merge. Cells can only be combined
across columns. When you merge cells, only the data in the first cell is
preserved. If data exists in other cells, the data is removed. Merged cells
can be split into their original columns.

See http://msdn2.microsoft.com/en-us/library/ms159169.aspx for more
information.

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