Where of a relative date

Hi gurus,

I need to count the number of events ending tomorrow.

[Tomorrow] =RelativeDate([Day] In Report;1)

[Day] is the prompted day. I have tried:

=[Event] Where([End date] = [Tomorrow]) and got #MULTIVALUE. Count of this, obviously is 0. [Event] and [End date] are dimensions. [Day] is a measure.

Thanks in advance,

Jonás