The short answer is: you can't. Editing an inserted image isn't at all difficult, though. For example, without knowing whether you're pasting in-line or wrapped, the following code will work with whatever you paste. Simply adjust the parameters to suit.
Code:
Sub Demo()
Dim Rng As Range
Set Rng = Selection.Range
With Rng
.Paste
If .ShapeRange.Count = 1 Then
With .ShapeRange(1)
.LockAspectRatio = msoTrue
.Width = InchesToPoints(4)
With .PictureFormat
.CropBottom = InchesToPoints(0.75)
.CropTop = InchesToPoints(0.75)
.CropLeft = InchesToPoints(1)
.CropRight = InchesToPoints(1)
End With
End With
ElseIf .InlineShapes.Count = 1 Then
With .InlineShapes(1)
.LockAspectRatio = msoTrue
.Width = InchesToPoints(4)
With .PictureFormat
.CropBottom = InchesToPoints(0.75)
.CropTop = InchesToPoints(0.75)
.CropLeft = InchesToPoints(1)
.CropRight = InchesToPoints(1)
End With
End With
End If
End With
End Sub