Hi Suzanne, this is absolutely possible, I actually have a feature just like this in one of our projects
What this code does is: check to see if there are any rows in a table named "Monthly Allocation Validation Transform", pulling unique values from an arbitrarily selected column for rows have a have a specific "DataSrc" value, and if there are any rows that match that criteria, it will display a warning if there are rows in the table with that value
I am not sure what type of code you are trying to put in this if statement, but this should enable you to make it work
The code is:
<span class = "top">
<%=if(eval("UniqueValues(Monthly_Allocation Validation Transform:Key[DataSrc=1])")="","","WARNING: The following CC Allocations do not amount to 100% </br> Please do not proceed until this is resolved </br>")%>
</span>
Let me know if this helps, or I need to explain it further!
Best,
Maxwell