'change the value of c in line 4 to match the col. you need
Sub check_dates()
Dim r As Integer
Dim c As Integer
r = 1: c = 1 'change c to correspond to your column
Do Until Cells(r, c) = ""
If IsDate(Cells(r, c)) = False Then
MsgBox ("cell " + Cells(r, c).Address + " is not of a date format")
Else
End If
r = r + 1
Loop
End Sub