how to change output file name vbs

i have a script that i am working with and i need the output file to be something like cert_computername.csv i have tried many suggestions and cant get it to work just right, currently it just outputs Certificates.csv

Option Explicit
Dim oTrans
Set oTrans = CreateObject("Scripting.FileSystemObject")
Dim oTransF
Set oTransF = oTrans.OpenTextFile("Certificates.csv", 2, True)
Dim objMMC
Set objMMC = CreateObject("MMC20.Application")
objMMC.Show
objMMC.Load("\\servername\Certificates\certmgr.msc")
Dim objDoc
Set objDoc = objMMC.Document
Dim objSN
Set objSN = objDoc.ScopeNamespace
Dim objRoot
Set objRoot = objDoc.RootNode
Dim objEvtVwrNode
Set objEvtVwrNode = objSN.GetChild(objRoot)
objSN.Expand(objEvtVwrNode)
Dim objView
Set objView = objDoc.ActiveView
On Error Resume Next
Dim objNode
Set objNode = Nothing
Set objNode = objSN.GetChild(objEvtVwrNode)
If (objNode Is Nothing) then
 Wscript.echo "Unable to get Event Viewer child node, end of programm."
 Wscript.quit
End If
Do Until (objNode Is Nothing)
 objSN.Expand(objNode)
 objView.ActiveScopeNode = objNode
 Dim BerDoss
 Set BerDoss = Nothing
 Set BerDoss = objSN.GetChild(objNode)
 Do Until (BerDoss Is Nothing)
  objSN.Expand(BerDoss)
  objView.ActiveScopeNode = BerDoss
  Dim objList
  Set objList = objView.ListItems
  Dim objItem
  For Each objItem In objList
   Dim str
   str = objView.CellContents(objItem, 1)
   If (str <> "Error") Then
    Dim vLigne
    Dim I
    vLigne = objNode.Name + " ; " + BerDoss.Name
    For I = 1 To 20
     vLigne = vLigne + " ; " + objView.CellContents(objItem, I)
    Next
    oTransF.writeline vLigne
   End If
  Next
  Dim objSib2
  Set objSib2 = Nothing
  Set objSib2 = objSN.GetNext(BerDoss)
  Set BerDoss = objSib2
 Loop
 Dim objSib
 Set objSib = Nothing
 Set objSib = objSN.GetNext(objNode)
 Set objNode = objSib
Loop
oTransF.Close
MsgBox "finished certs"
Wscript.quit

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