2 conditions from 2 datasets in expression of row visibility

Hi Experts,

In ssrs, I want to create an expression for the row visibility. But, the expression will contain 2 conditions from different 2 datasets. I have created an expression, but it does not pass in SSRS. The error message is
"The Hidden expression for the tablix ‘Tablix9’ refers to the field ‘launchdate’.  Report item expressions can only refer to fields within the current dataset scope or, if inside an aggregate, the specified dataset scope. Letters in the names of fields must use the correct case."

Can some one help me to correct it?  Thank you.

=iif (monthname(month(today()))= Last(Fields!MonthName.Value, "DealStarts") or (Fields!launchdate.Value, "RowofTrendingVisibility")>=Parameters!StartDate.Value, true, false)
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ValentinoVBI ConsultantCommented:
As you have discovered you cannot refer to two different datasets like that.  The only option is using the lookup functions.  Have a read through following article for details, let us know if after that you need further help: Looking Up Data On Different Sources
tanj1035Author Commented:
Thanks, ValentinoV, I read your article which is very good. But, I do not how I can apply it to my question.
Nico BontenbalCommented:
Depending on your data you might also be able to use the scope parameter of an aggregate function to get the data for the other recordset. See:
This is less complex than the Lookup function.

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