How do I resize an inserted image in a cell?

Hi all,
I have a problem that is driving me crazy. I'm pretty new to VBA/Macros. I have managed to get the macro working to insert a specific jpeg image into the right cell 'W28', however I don't know how to resize the image so that it doesn't cross over the cell borders, which it currently does. The macro is linked to a command button. There will be a few buttons, each one inserting a different signature depending on the user. Once I have the first one sorted, then it will be straight forward to do the others. Here is the code I currently have;

Sub InsertPictureIG()
    InsertPictureAInRange "C:\Users\Chief Engineer\Documents\Engine Room Log\Signatures\Benn Signature.jpg", _
    Range("W28")
End Sub

Sub InsertPictureAInRange(PictureFileName As String, TargetCells As Range)
     ' inserts a picture and resizes it to fit the TargetCells range
    Dim p As Object, t As Double, l As Double, w As Double, h As Double
    If TypeName(ActiveSheet) <> "Worksheet" Then Exit Sub
    If Dir(PictureFileName) = "" Then Exit Sub
     ' import picture
    Set p = ActiveSheet.Pictures.Insert(PictureFileName)
     ' determine positions
    With TargetCells
        t = .Top
        l = .Left
        w = .Offset(0, .Columns.Count).Left - .Left
        h = .Offset(.Rows.Count, 0).Top - .Top
    End With
     ' position picture
    With p
        .Top = t
        .Left = l
        .Width = w
        .Height = h
    End With
    Set p = Nothing
End Sub

Can someone please help me on this?

Thanks,
Benn