Date Filter For Listbox

I have a list details in ranges "CV:DC" column CV has date entries so with the code given above i just select the date from combo box and check the details by pressing command button..Actually this code is doesn't work with combo box but it works with textbox except date data entries in
this mode.
So how can i improve this option if im going to use it in combo box.

Private Sub CommandButton26_Click()
Dim a, i As Long, ii As Long, b(), n As Long
ListBox4.Clear
With ComboBox6
If .Text = "" Then Exit Sub
If WorksheetFunction.CountIf(Range("cv:cv"), .Text) = 0 Then
MsgBox "Bad Data"
Exit Sub
End If
a = Range("cv1", Range("c" & Rows.Count).End(xlUp)).Resize(, 8).Value
For i = 1 To UBound(a, 1)........................