VB 2010 compare string within directory and store latest revision letter of the file name - vb.net

Question

My application currently extracts data from an excel document, putting the data into a listview. I then am able to open each of the strings/items within the listview (which are pdf files in a given directory). However the pdf files within the given directory have revision letters at the end of their file names, starting with 'A' for the first revision and 'B' for the second revision...and so on.
So I am trying to approach it like comparing the string to the files in the directory and then once it's found, check what the latest rev letter is if any.
So if there is 07010302A.pdf file in the directory and there's also a 07010302B.pdf in the directory, I want to store that file name (07010302B.pdf) to a new string in my vb application. Any help on this would be much appreciated.
Here's what I am working with:
Imports Excel = Microsoft.Office.Interop.Excel
Public Class Form1
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
Dim xlApp As Excel.Application
Dim xlWorkBook As Excel.Workbook
Dim xlWorkSheet As Excel.Worksheet
Dim range As Excel.Range
Dim rCnt As Integer
Dim cCnt As Integer
Dim Obj As Object
xlApp = New Excel.Application
xlWorkBook = xlApp.Workbooks.Open("C:\Users\Admin\Desktop\Exp_Master.xlsm")
xlWorkSheet = xlWorkBook.Worksheets("Sheet1")
range = xlWorkSheet.Range("H1:H100") 'xlWorkSheet.UsedRange
For rCnt = 1 To range.Rows.Count
For cCnt = 1 To range.Columns.Count
Obj = CType(range.Cells(rCnt, cCnt), Excel.Range)
If IsNumeric(CType(range.Cells(rCnt, cCnt), Excel.Range).Value) Then
'MsgBox(Obj.value)
ListView1.Items.Add(Obj.value)
ListView1.View = View.List
End If
Next
Next
xlWorkBook.Close()
xlApp.Quit()
releaseObject(xlApp)
releaseObject(xlWorkBook)
releaseObject(xlWorkSheet)
'Kill Excel Process that wouldn't close
Process.Start("C:\Users\Admin\Desktop\batch archive\EXCEL_KILLER.bat")
'MsgBox("Total Item(s) in ListView:" & ListView1.Items.Count)
Dim i As Integer = 0
Dim n As Integer = 0
Dim str As String
For i = 1 To (ListView1.Items.Count)
Dim strng As String = "R:\"
n = (i - 1)
str = strng & (ListView1.Items.Item(n).Text) & (".pdf")
MsgBox(str)
'----
'System.Diagnostics.Process.Start(str)
'Here I want to check the R:\ directory and compare it with each string to see
'what the latest revision letter of the filename is and store it in another string to add to
'a pdf merging list later in this for loop
'----
Next
End Sub
Private Sub releaseObject(ByVal obj As Object)
Try
System.Runtime.InteropServices.Marshal.ReleaseComObject(obj)
obj = Nothing
Catch ex As Exception
obj = Nothing
Finally
GC.Collect()
End Try
End Sub
End Class

Answer 1

I was able to use your Directory.getfiles suggestion and I added a for loop to display only the last of the files labeled within that criteria. Thanks a bunch, just took a little more playing with it to determine what I actually wanted and how to put it in code.
If anyone cares, here is the update that works and gets the last file name and path of the directory.getfiles group within a search criteria.
Cheers!
For i = 1 To (ListView1.Items.Count)
Dim strng As String = "R:\"
n = (i - 1)
str = strng & (ListView1.Items.Item(n).Text) & (".pdf")
'MsgBox(str)
Dim substr As String
substr = str.Substring(3, 8)
'MsgBox(substr)
'----
'System.Diagnostics.Process.Start(str)
' Only get files that begin with...
Dim dirs As String() = Directory.GetFiles("R:\", (substr & ("*.pdf")))
'MsgBox("The number of files starting with your string is {0}.", dirs.Length)
Dim dir As String
For Each dir In dirs
If dir Is dirs.Last Then
MsgBox(dir)
'do something with your last item'
End If
Next
'----
Next
End Sub