First off, I have to say I'm not entirely sure what you have going on with some of the formulas, or where some of the data in the green fields was used.
With that said, this should at least get you on the right track.
Firstly, I moved your Total Losses for Bends, and the total of column L to Row 12, then started the table headers on row 13, and the first line of data will be on row 14. This makes it easier to update the total for column L.
You can also add some formatting to the new rows for the reducer table if you so wish to have a border.
I simply put this code in an ActiveX Command Button on the form.
Private Sub Testing_Click()
Dim lastRow As Long
lastRow = .Cells(.Rows.Count, "F").End(xlUp).Row + 1
'set the data in the Reducer table.
.Range("F" & lastRow) = "Reducer " & lastRow - 13
.Range("G" & lastRow) = .Range("B5")
.Range("H" & lastRow) = .Range("B4")
.Range("I" & lastRow) = .Range("B9")
.Range("L12").Formula = "=Sum(L14:L" & lastRow & ")"
'clear the input area
.Range("B4") = ""
.Range("B5") = ""
'move the active cell back to B4 to input more data