how to use library?

i use below code to check my external storage. maybe this is not the correct way but this is work! if who have any better solution please tell me.

for my system almost every form using this code, so i hope can use library to write this code, it is easy for me if next time i want modify the code. but i never use library before so i hope someone else can help me or give me some example to refer.

Private Shared Dir As IO.Directory
Private Shared myStr1 As String = "Directory, Temporary"
Private Shared Directories() As String = Dir.GetDirectories("\")
Private Shared i As Long
Private Shared DirInfo As IO.DirectoryInfo
Private Shared FileInfo As IO.FileSystemInfo
Dim myComp As CompareInfo = CultureInfo.InvariantCulture.CompareInfo
Try
For i = 0 To Directories.Length - 1
FileInfo = New IO.DirectoryInfo(Directories(i))
Dim myStr2 As String = FileInfo.Attributes.ToString()
If myComp.Compare(myStr1, myStr2) = "0" Then
'if compare is true that mean it is external storage, so what should i write here to store avaiable external storage so that i can call it from library to my system.
End If
Next
Catch ex As Exception
MsgBox("No storage card found.")
End Try

my english is poor, sorry! if have any question please tell me.