Picking Correct File From Folder

I need to look at each filename in a particular folder, open the file if the name contains "THO", then modify the file and close it. I know how to open, modify, and close files using VBA. I'm stuck on how to pick one particular file based on the filename. I copied the code below from another thread. It's great for opening all files in the specified directory. Can anyone show me how to modify it so I only open files with "THO" in the name?

Sub OpenWorkbooks()
Dim wb As Workbook
Dim dirr As String
Dim I As Long
Application.DisplayAlerts = False
dirr = "C:Documents and SettingsHalldaviDesktopKoen's weekly sample reports"
With Application.FileSearch
.NewSearch
.LookIn = dirr
.FileType = msoFileTypeExcelWorkbooks
.SearchSubFolders = False
.Execute
For I = 1 To .FoundFiles.Count
Set wb = Workbooks.Open(.FoundFiles(I))
Next I
End With
End Sub