ssrs Sum IIF with multiple datasets

HI,

Im trying to create a Sum IIF expression with multiple datasets, is this possible?

the below expression is from one dataset (I basically need the same sum into the second table)

=Sum(IIF(Fields!Non_Billable.Value = False, 0, IIF(Fields!Adjustment.Value = False, Fields!Used_Units.Value, Fields!Used_Units_Adj.Value)))

Now, the tricky part is to use the above expression in a second table with a second dataset, i have tried the following:

=IIF(Fields!Non_Billable.Value = True, IIF(Fields!Adjustment.Value = False, Fields!Used_Units.Value, Fields!Used_Units_Adj.Value, "DataSet1"),0), "DataSet1")

Any suggestions?

Thank you