modifying csv file using vba - excel

Question

I need help in modifying the CSV file using VBA. I did research and came up with this solution. However, I can't get the expected output. So, for example, I have a CSV file:
ProductID,ProductName,SupplierName,CategoryID,Unit,Price
,,,,,
1,Chais,John Ray,1,10 boxes x 20 bags,18.00093483
2,Chang,Michael,1,24 - 12 oz bottles,19.66890343
I want to change all the values under the productname and suppliername. And change something like the combination of ProductID and the Column Name. My expected output should look like:
ProductID,ProductName,SupplierName,CategoryID,Unit,Price
,,,,,
1,1 ProductName,1 SupplierName,1,10 boxes x 20 bags,18.00093483
2,2 ProductName,2 SupplierName,1,24 - 12 oz bottles,19.66890343
It can occur multiple times and can change the column location. This is my code:
Sub test()
Dim FilePath As String, LineFromFile As Variant, LineItems() As String, strFile As Variant
FilePath = "C:\Users\mestrivo\Documents\Files\MyFirstProg\test.csv"
Open FilePath For Input As #1
Do Until EOF(1)
Line Input #1, LineFromFile
LinteItems = Split(LineFromFile, ",")
LineItems(1) = LineItems(0) & " ProductName"
LineItems(2) = LineItems(0) & " SupplierName"
strFile = Join(LineItems, ",")
Loop
Open "C:\Users\mestrivo\Documents\Files\MyFirstProg\test - 2.csv" For Output As #1
Print #1, strFile
Close #1
End Sub
Please help me check my code. I got an error on this part:
Open "C:\Users\mestrivo\Documents\Files\MyFirstProg\test - 2.csv" For Output As #1
it says that the file is already open.

Answer 1

NEVER hard-code file handles, they aren't for you to grab, they're for VBA to query what's available and give you a free, usable file handle. Use the FreeFile function to do this.
Dim fileHandle As Long
fileHandle = FreeFile
Then replace all hard-coded #1 handles with #fileHandle.
You cannot open two different files using the same handle. You've already opened the file for input:
Open FilePath For Input As #1
So when you try to use the same handle for output...
Open "C:\Users\mestrivo\Documents\Files\MyFirstProg\test - 2.csv" For Output As #1
That's when you get an error; you haven't closed the #1 handle yet, and now you're trying to reuse it to open another file - you can't do that.
You're dealing with two files, so either you open the first one, read it, then close it before you open the second one, write to it and then close it - or, you open both, and write to one as you read the other, then close both.
Either way, you shouldn't hard-code file handles. Use FreeFile to get a free file handle. Always.

Answer 2

Try this:
Sub test()
Dim FilePath As String, LineFromFile As Variant, _
LineItems() As String, strFile As Variant
FilePath = "mycsv.csv"
Open FilePath For Input As #1
Do Until EOF(1)
Line Input #1, LineFromFile
LineItems() = Split(LineFromFile, ",")
'I suggest to add the following 'If' statements
If LineItems(0) <> "" Then
LineItems(1) = LineItems(0) & " ProductName"
LineItems(2) = LineItems(0) & " SupplierName"
End If
If strFile <> "" Then strFile = strFile & Chr(10)
'-------------------------------------------------
strFile = strFile & Join(LineItems, ",")
Loop
'In the next 'Open' statement you are trying to
'assign an object over another that's already opened,
'therefore you must close the previous object first
'and / or declare the second one with another name
Close #1
Open "mycsv2.csv" For Output As #1
Print #1, strFile
Close #1
End Sub