How can I tell macro to perform operations below "= vbNo Then" ?

Hey Greg Bonaparte 

So, what you have to do is to make an "ElseIf" statement for vbNo, and and "Else" statement for the when you press cancel. 

Here is the code I used (I just used "a" as a variable for the Messagebox):

Sub OPTIMIZE()

a = MsgBox("OPTIMIZE AWSORT FOR A MINIMUM OF TWENTY-FOUR INSTRUMENTS. HAVE YOU COMPLETED OPTIMIZATION?", vbQuestion + vbYesNoCancel, "HonorSystem24")

If a = vbYes Then
Call Combo_MacroLessThan4k

ElseIf a = vbNo Then

ActiveWindow.ScrollRow = 624
Range("V13:V14").Select
Selection.Copy
Range("V640:V641").Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
Range("W13:W14").Select
Selection.Copy
Range("W640:W641").Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
Range("X13:X14").Select
Selection.Copy
Range("X640:X641").Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
Range("Y13:Y14").Select
Selection.Copy
Range("Y640:Y641").Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
Range("Z13:Z14").Select
Selection.Copy
Range("Z640:Z641").Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
Range("AA13:AA14").Select
Selection.Copy
Range("AA640:AA641").Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
Range("V13:Z14").Select
Selection.ClearContents

Else
Exit Sub
End If
End Sub