Multiple dataset calculation

I have 3 tables pulling data from 3 different datasets. In my 3rd table i need to sum the table1-column2 to table2-column3.

e.g.

=Fields!Column2.Value,"Dataset1"+(Fields!Column3.Value, "Dataset2")

This does not work.

Please help.

You cannot do cross-dataset operations except at an aggregate level, i.e.

=Fields!Column2.Value+Sum(Fields!Column3.Value, "Dataset2")