No. The ColSpan property can't be changed using an expression. SorryPaul Turley, MVP [Hitachi Consulting] SQLServerBIBlog.com *Please vote if helpful*

Laelaf - Would you mind posting an example or more detail of what you are trying to accomplish? Generally speaking, you can use expressions to merge fields within a single column, but not for merging columns. That said, you should be able to give the appearance conditionally splitting/merging text boxes based on expressions and some creative thinking...

Is that possible to merge adjacent cells conditionally in SSRS 2008? For Example Col A ColB Col C ColD ColE ColF If condtion is true ColC and Col D to be under Col A and ColE and Colf to be under Col B Or Col C to be under Col ColA and Cold to ColF to be undercol B

You should be able to accomplish the example by creating a second row within the row group, then use an expression to hide the merged rows when condition is false...an example is below.. Condition for top row: Condition for second row: The result when run...