VBA - Trouble with Loop Structure for File Searching and Copying - vba

Question

I'm trying to develop a macro on one of my spreadsheets that will take the value of Column B (2502-13892-33 for example), starting at Row 3, and search the source folder listed in column A for that file (using Wildcards before and after the value in column B. Once it finds that file, it needs to use FileCopy to copy the file into the Destination Folder listed in Column C, but only after renaming the file in the form of "Column E"_"Original Filename (A252_2502-13892-33 for example).
I think I have worked out the code to make this work because when I tested it, it functioned exactly like I expected it to, found the file, copied it to the new destination with the PREFIX from column E and the underscore added to the filename. The problem is that it just stops after the first file, which leads me to believe something is wrong with the structure of my loop.
My code is as follows:
Sub MoveFiles()
Dim SourcePath As String
Dim DestPath As String
Dim PartNum As String
Dim PLISN As String
Dim LastRow As Long
Dim i As Long
Dim filename As String
LastRow = Cells(Rows.Count, "A").End(xlUp).Row
For i = 3 To LastRow
PLISN = Cells(i, "E").Value
PartNum = Cells(i, "B").Value
If Right(Cells(i, "A").Value, 1) <> Application.PathSeparator Then
SourcePath = Cells(i, "A").Value & Application.PathSeparator
Else
SourcePath = Cells(i, "A").Value
End If
If Right(Cells(i, "C").Value, 1) <> Application.PathSeparator Then
DestPath = Cells(i, "C").Value & Application.PathSeparator
Else
DestPath = Cells(i, "C").Value
End If
If Dir$(SourcePath & "*" & PartNum & "*") = "" Then
Cells(i, "D").Value = "Source file does not exist."
ElseIf Dir$(DestPath & PLISN & "_" & "*" & PartNum & ".pdf") <> "" Then
Cells(i, "D").Value = "File already exists."
Else
filename = Dir$(SourcePath & "*" & PartNum & "*" & ".pdf")
'Copy the file
FileCopy SourcePath & filename, DestPath & PLISN & "_" & filename
Cells(i, "D").Value = "File Copied to new location"
End If
Next i
End Sub

Answer 1

I had accidentally left my DestinationPath blank for the 2nd and 3rd lines of the excel sheet. That was what was giving me just the "\" as the destination path. Seems to be working properly now.
As someone mentioned below in one of the comments, stepping through my code in the debugger was extremely helpful to solving this problem. My final code has some structural changes, in that I no longer have columns for SourcePath and DestPath, and instead use a folder dialog box to have the user select both of those.
The code for selecting my Source and Destination Folders:
Sub SourceFolder()
Dim lCount As Long
Dim rCount As Long
SourcePath = vbNullString
DestPath = vbNullString
With Application.FileDialog(msoFileDialogFolderPicker)
.InitialFileName = OpenAt
.Title = "Source Path"
.Show
For lCount = 1 To .SelectedItems.Count
SourcePath = .SelectedItems(lCount)
MsgBox (SourcePath)
Next lCount
End With
With Application.FileDialog(msoFileDialogFolderPicker)
.InitialFileName = OpenAt
.Title = "Destination Path"
.Show
For rCount = 1 To .SelectedItems.Count
DestPath = .SelectedItems(rCount)
MsgBox (DestPath)
Next rCount
End With
End Sub
The code for actually going out to the SourcePath, searching for the filename located in Column A (including with wildcards before and after), copying it to the DestinationPath, and renaming it with ColumnB's Value, followed by an underscore, and then ColumnA's Value is as follows:
Option Explicit
Public SourcePath As String
Public DestPath As String
Dim PartNum As String
Dim PLISN As String
Sub MoveFiles()
Dim LastRow As Long
Dim i As Long
Dim filename As String
LastRow = Cells(Rows.Count, "A").End(xlUp).Row
For i = 3 To LastRow
PLISN = Cells(i, "B").Value
PartNum = Cells(i, "A").Value
If Right(SourcePath, 1) <> Application.PathSeparator Then
SourcePath = SourcePath & Application.PathSeparator
Else
SourcePath = SourcePath
End If
If Right(DestPath, 1) <> Application.PathSeparator Then
DestPath = DestPath & Application.PathSeparator
Else
DestPath = DestPath
End If
If Dir$(SourcePath & "*" & "*" & PartNum & "*") = "" Then
Cells(i, "C").Value = "Source file does not exist."
ElseIf Dir$(DestPath & PLISN & "_" & "*" & PartNum & "*" & ".pdf") <> "" Then
Cells(i, "C").Value = "File already exists."
Else
filename = Dir$(SourcePath & "*" & PartNum & "*" & ".pdf")
'Copy the file
FileCopy SourcePath & filename, DestPath & PLISN & "_" & filename
Cells(i, "C").Value = "File Copied to new location"
End If
Next i
End Sub