VBA Lookup in Another Workbook - vba

Question

I am having an vba problem with Excel. So I have this workbook, "Book Tool - Updated Feb. 2017.xlsb", that I am currently updating and will distribute to about 10 team members to use to keep track of their work. What I am trying to do is lookup data from an outside document, "Team Data", put that in Column DE of the "Book Tool - Updated Feb. 2017.xlsb" file. So I wrote the below code, where when the team member pushes a button, it opens up the lookup file, looks for the data in Column A of the "SICcode" sheet of that external file, matches it with Column B of the "Book Sheet" of the "Book Tool" file, and returns the value in Column D of the lookup file. It runs for the length of the "Book Sheet", closes the external file, and you get a popup that the data add is done.
Now when I did this code myself, it works great. Automatically opened the external document, did the lookups, returned the correct value, closes the external document, the pop up. So I sent the file with the macro to my manager to play around with before giving it to the rest of my team, but the macro does not work. When the macro runs, the external document opens, it seems like it is running through the lookups, closes the external file, and the pop up appears, but there is no value in the DE column, nor is there the lookup formula there. My manager didn't change the name of the Tool document, he didn't mess with any code. He emailed it back to me and with that copy the formula isn't working, but I checked it with my master copy formula and even though it's the same, the macro will not populate the data.
We have to keep the external data in a separate file, because otherwise the tool with the lookup data is over 2MB and takes forever to run or crashes.
Is there something about emailing the tool back and forth that messes with the file, or is there some formatting issue I need to look into that causes it not to work? With my master copy on my computer, the code always works regardless if I work in a virtual desktop, have it in a different folder, whatever.
I am just okay with vba, I don't know all of the technicalities of this process, so maybe I am overlooking some flaw with how I've set it up or limitations Excel has. Any guidance or help would be appreciated.
Sub AddData()
On Error Resume Next
'Open External Data Source
Workbooks.Open Filename:= _
"W:\USB\Reporting\Book Tool\Attachments\Team Data.xls"
'View sheet where data will go into
Windows("Book Tool - Updated Feb. 2017.xlsb").Activate
'Gets last row of Tool sheet
Sheets("Book").Select
lastrow = Cells(Rows.Count, "B").End(xlUp).Row
'Lookup in External File
Sheets("Book").Select
Range("DE2:DE" & lastrow).FormulaR1C1 = "=VLOOKUP(RC[-108],'[Team Data.xls]SICcode'!C[-109]:C[-104],5,FALSE)"
'Close External Data File
Windows("Team Data.xls").Activate
ThisWorkbook.Saved = True
Application.DisplayAlerts = False
ActiveWindow.Close
MsgBox "Data Add Done"
End Sub

Answer 1

Be sure to properly qualify your statements, and also it would be wise to assign the appropriate workbook to a variable. See the modified code below:
Sub AddData()
On Error Resume Next ' I also suggest removing this since it wont warn you on an error.
Dim wb as Workbook
Dim wbExternal as Workbook
Dim ws as Worksheet
Dim wsExternal as Worksheet
'Open External Data Source
Set wbExternal = Workbooks.Open Filename:= _
"W:\USB\Reporting\Book Tool\Attachments\Team Data.xls"
' Depending on the location of your file, you may run into issues with workbook.Open
' If this does become an issue, I tend to use Workbook.FollowHyperlink()
'View sheet where data will go into
' Windows("Book Tool - Updated Feb. 2017.xlsb").Activate
' Set wb = ActiveWorkbook
' As noted by Shai Rado, do this instead:
Se wb = Workbooks("Book Tool - Updated Feb. 2017.xlsb")
' Or if the workbook running the code is book tool
' Set wb = ThisWorkbook
'Gets last row of Tool sheet
Set ws = wb.Sheets("Book")
lastrow = ws.Cells(ws.Rows.Count, "B").End(xlUp).Row
'Lookup in External File
Set wsExternal = wbExternal.Sheets("Book")
wsExternal.Range("DE2:DE" & lastrow).FormulaR1C1 = "=VLOOKUP(RC[-108],'[Team Data.xls]SICcode'!C[-109]:C[-104],5,FALSE)"
'Close External Data File
ThisWorkbook.Saved = True
Application.DisplayAlerts = False
Windows("Team Data.xls").Close
MsgBox "Data Add Done"
End Sub
I would also recommend browsing through SO for tips on avoiding .Select and .Activate as this can make your code unreliable and in some cases can slow down your code significantly.
Lastly, if performance is a concern you may want to look into loading your lookup values into arrays and finding the corresponding values this way. It will completely depend on what kind of data you are working with. I had a workbook using filldown vlookups that went from running in a matter of 5-10 minutes or more to consistently running in less than 20 seconds by replacing VLOOKUPS with for looping arrays.