ok from what I see the file looks like this:

Code:
LastName
FirstName
CustomerNumber
LastName
FirstName
CustomerNumber
...
This should do the trick:

VB Code:
  1. Public Structure Customer
  2.         Dim LastName As String
  3.         Dim FirstName As String
  4.         Dim CustomerNumber As String
  5.     End Structure
  6.  
  7.     Public Function FindCustomer(ByRef CustomerInfo As Customer) As Boolean
  8.         Dim sr As New System.IO.StreamReader("Database.txt")
  9.  
  10.         Dim strFile() As String = Split(sr.ReadToEnd, vbCrLf)
  11.  
  12.         Dim I As Integer
  13.  
  14.         For I = 0 To strFile.GetUpperBound(0) Step 3 ' Stepping 3 always makes sure we land on a last name
  15.             If strFile(I).ToUpper = CustomerInfo.LastName.ToUpper Then
  16.  
  17.                 CustomerInfo.FirstName = strFile(I + 1)
  18.                 CustomerInfo.CustomerNumber = strFile(I + 2)
  19.                 'we found what we were looking for now lets not waste any time :D
  20.                 Return True
  21.             End If
  22.  
  23.         Next
  24.  
  25.     End Function

now to use this:

VB Code:
  1. 'Put this in ur btnSearch's Click event
  2.         Dim CustomerToFind As Customer
  3.  
  4.         CustomerToFind.LastName = InputBox("Please Type Customer Name: ", "Find Customer")
  5.  
  6.         If FindCustomer(CustomerToFind) = True Then
  7.             'We Found a Customer
  8.             MsgBox(CustomerToFind.LastName & ", " & CustomerToFind.FirstName & " was Found!" & vbCrLf & _
  9.                 "Customer Number: " & CustomerToFind.CustomerNumber, MsgBoxStyle.Information, "Customer Found!")
  10.         Else
  11.             MsgBox("Customer not Found!")
  12.         End If