Find row number from value in combobox by searching sheet

I need to find the row number on a sheet by searching for a value from the combo box. I have created a calender that lists dates that are free in the combo box and then details need to put inputted in the same row. I've written this code and used a messagebox to test that the row is correct, but it just shows 0. This is the code i've written, not sure if im on the right lines..

Private Sub BookButton_Click()
Dim i As Integer
Dim r As Integer
Dim Datev As String
Dim w As Worksheet

Set w = Worksheets("Calender")

Datev = ComboBox1.value

For i = 3 To w.Cells(Rows.Count, "B").End(xlUp).Row
   If w.Cells(i, 2) = Datev Then
End If: Next i

i = r
MsgBox (r)

End Sub