|You might be able to use a Worksheet_Change macro.|
The macro would monitor changes to the working sheet and if a value is entered in the quantity column, it could copy the description to the quote sheet.
That part is fairly easy:
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Column = 2 And Target.Cells.Count = 1 Then
nxtRow = Sheets("Quotation").Range("A" & Rows.Count).End(xlUp).Row + 1
Target.EntireRow.Copy Destination:=Sheets("Quotation").Range("A" & nxtRow)
The harder part comes with dealing with changes to the quantity, or deletion of an item or other changes that you might want to make while building the quote.
Since my "simple" code is going to copy the row whenever a change is made to the quantity, you'll get duplicates if you change the quantity or even delete the number.
We would need to know exactly how you plan to deal with chnages like that before we could offer any more suggestions.