Editing BOM automatically

Thanks,

Please take a look at the original spread sheet that Inventor spits out, I`m using macros (Ctrl+shift+F) to change it a little bit. Then if you run the macro below it will add 2 rows between materials...
My question is how to add WEIGHT: in F column and sum weight in G column???

Sub detect_mat()
Dim last As Long
Dim x As Long
last = Cells(Rows.Count, "e").End(xlUp).Row
For x = 3 To last * 4 Step 1
If Cells(x, 5).Value <> Cells(x + 1, 5).Value Then
Rows(x + 1).Select
    Selection.Insert Shift:=xlDown, CopyOrigin:=xlFormatFromLeftOrAbove
    Selection.Insert Shift:=xlDown, CopyOrigin:=xlFormatFromLeftOrAbove
    x = x + 2
    'HOW TO ADD WEIGHT?
    'HOW TO ADD SUM WEIGHT?
End If
Next
End Sub