Goto Expressions :

iif(fields!country.value="","",<field_name>,<field_name>)

Not sure about your requirement in real time .

You can input the date from calendar , instaed of static value ,let it be dynamic !!!

You can try using component named script component

Code for you reference :

Dim keyField As Integer = Row.KeyField

Dim itemList As String = Row.ListField

...