VBA Autofilter Syntax

I am trying to get the below autofilter working but to no avail, its just putting the text datStart and datEnd in the auto filter, not what I receive in the boxes, see bold line for line in question

Dim datStart, datEnd As Date
Dim strAgent As String
datStart = txtStart.Value
datEnd = txtEnd.Value
strAgent = txtAgent.Text
Range("A4").Select
Selection.AutoFilter
Selection.AutoFilter Field:=4, Criteria1:=">datStart", Operator:=xlAnd, _
Criteria2:="<datEnd"