IsNull for Date works in a table but not in bar chart or KPI

[JacobJones]

So if I include:

=if(IsNull([Date of Appointment]), [Date of Appointment])

In a table, it only returns many records  that have a null Date of Appointment

However, if I try and use it as a measure:

=count(if(IsNull([Date of Appointment]), [Date of Appointment]))

it counts zero. 

Any ideas?

[Vegar · Accepted solution]

Try to use 

=NullCount([Date of Appointment])

[JacobJones]

Thank you so much, that did the trick.