Importing emails and subject line

you want to run it from outlook and udpate an existing excel file with the info from outlook ?
or
you have an excel file that is going to lookup the email in outlook to get the info ?

This should get you on the way
place it in a fresh module in your Outlook VBA session
then select an email and then run the sub GetSelectedItem (added)

Private Sub GetSelectedItem()
    Dim oApp As New Outlook.Application
    Dim oExp As Outlook.Explorer
    Dim oSel As Outlook.Selection
    Dim oItem As Object
    Set oExp = oApp.ActiveExplorer
    Set oSel = oExp.Selection
    For i = 1 To oSel.Count
        Set oItem = oSel.Item(i)
        DisplayInfo oItem
    Next i
End Sub
Sub DisplayInfo(oItem As Object)
    Dim oMailItem As Outlook.MailItem
    Set oMailItem = oItem
        Set excApp = CreateObject("Excel.Application")
        Dim strSheet As String
        strSheet = "c:\your file location here\...xls"  '''''''''''''update location'''''''''''''''
        excApp.Workbooks.Open (strSheet)
        Set excWkb = excApp.ActiveWorkbook
        Set excWks = excWkb.ActiveSheet
        excApp.Visible = True
        excWks.Activate
        With excWks
            .Cells(1, 1) = oMailItem.Subject
            .Cells(1, 3) = oMailItem.ReceivedTime
            .Cells(1, 4) = oMailItem.Body
        End With
End Sub