VBA code: automplete a column from a list of items in a different sheet

I would like to autocomplete columns G and H from lists in columns A and B of sheet 2, respectively. I am a biologist and know absolutely NOTHING about VBA. I found some code that should serve my purpose for one of the two items. But I have no idea how to adapt it to our sheets, not even to autocomplete just one column. I would be very grateful if someone can do that for me. The code is at http://www.vbaexpress.com/kb/getarticle.php?kb_id=244
Private Sub Worksheet_Change(ByVal Target As Range)
'Sub "autocompletes" data entered into column A using a source table on a different worksheet. If more than one match is
' found, the user is allowed to continue entering characters until a unique match is found. If no matches are found, the
' data is accepted as entered. ALT + Enter, Enter to force the macro to accept data as entered. The sub is triggered by
' the Enter key.
Dim cel As Range, match1 As Range, match2 As Range, rg As Range, targ As Range

'***Please adjust the next two statements before using this code!***
Set targ = Intersect(Target, Range("A:A")) 'Watch the cells in column A
Set rg = Worksheets("Source data").Range("AutoCompleteText") 'Use named range AutoCompleteText for "autocomplete" info

If targ Is Nothing Then Exit Sub
Application.ScreenUpdating = False
Application.EnableEvents = False
On Error Goto errhandler 'If code encounters an error, turn events back on

For Each cel In targ
If Not IsError(cel) Then
If cel <> "" And Right(cel, 1) <> Chr(10) Then
Set match1 = Nothing
Set match1 = rg.Find(cel & "*", lookat:=xlWhole, MatchCase:=False) 'Match is case insensitive
If Not match1 Is Nothing Then
Set match2 = rg.FindNext(after:=match1)
If match2.Address = match1.Address Then 'Code is fooled by identical strings in two cells
cel = match1 'Only one match found. Use it to "autocomplete" the cell
Else 'More than one match found. User must enter more data. Return to "Edit" mode
cel.Activate
Application.SendKeys ("{F2}") 'Begin editing after last character entered
End If
Else 'No matches found. Do not change entered text
End If
Else 'Strip the line feed from the end of the text string
If cel <> "" And Right(cel, 1) = Chr(10) Then cel = Left(cel, Len(cel) - 1)
End If
End If
Next cel

errhandler: Application.EnableEvents = True
On Error Goto 0
Application.ScreenUpdating = True
End Sub