The If Then Else End If construct is not that difficult.  A Then is required
for every If.  An End If is always required for every If.  The Else is
optional.

If SomeCondition = True Then
   Take Actions provided the condition evaluates to True
Else
   Take Actions provided the condition does not evaluate to True
End If

I have modifed your code to give you a real life example.   Please notice
the indentation.  It makes conditional statements much easier to read.

If frmUpdateAcctList.Desc = "" Then
   If MsgBox("The Account Descriptions are Not Updated, " _
           & "Do you want to Update the Account List Later", _
           vbQuestion + vbYesNo) = vbYes Then
       msgbox "You will be asked to Update the Account List at a Later time"
       Docmd.Close
'The Line below is not correct.  I don't know what you are trying to do here
   Else
       docmd.query (for the items that were updated)
   End If
Else
   MsgBox "The Account List is Updated"
   Docmd.Requery
End If

Dim iResponse as Integer
Dim strMessage as String

If frmUpdateAcctList.Desc <> "" Then
    MsgBox "The Account List is Updated"
   Docmd.Requery
   Docmd.Close
Else
   '(If frmUpdateAcctList.Desc  = "" )
   strMessage =  "The Account Descriptions are Not Updated, Do you want to
Update the  Account List Later"
    iResponse = MsgBox (strMessage, vbYesNo)
   ' Begin 2nd nested If...Then structure. This statement completed (End
If) before you complete the current/first If...Then.
    If iResponse = vbNo Then
       ' Return to the form: i.e., do nothing
    Else
       ' Yes
         strMessage = "You will be asked to Update the Account List at a
Later time"
         Msgbox strMessage, vbOK
       docmd.query (for the items that were updated)
       docmd.close
   End If            'if iResponse = vbNo Then
End If                'If frmUpdateAcctList.Desc <> "" Then

HTH,

In addition to your other replies, Desc is a reserved Access/VBA/Jet
word and should not be used as a field or control name.
For additional reserved words, see the Microsoft KnowledgeBase article
for your version of Access:

109312  'Reserved Words in Microsoft Access'  for Access 97
209187  'ACC2000: Reserved Words in Microsoft Access'
286335  'ACC2002: Reserved Words in Microsoft Access'
321266  'ACC2002: Microsoft Jet 4.0 Reserved Words'