Show / Hide Sheets based off a cell input

I've seen several ways to hide sheets based off a determined value. The way I have been doing it is like the following:

Private Sub Worksheet_Change(ByVal Target As Range)
Dim sWord As Integer
sWord = Sheets("Master").Range("B8").Value

If sWord = "4" Then
    Sheets("CofA1").Visible = True
    Sheets("CofA2").Visible = True
    Sheets("CofA3").Visible = True
    Sheets("CofA4").Visible = True
    Sheets("CofA5").Visible = False
    Sheets("CofA6").Visible = False
    Sheets("CofA7").Visible = False
    Sheets("CofA8").Visible = False
    Sheets("CofA9").Visible = False
    Sheets("CofA10").Visible = False
    Sheets("CofA11").Visible = False
    Sheets("CofA12").Visible = False
    Sheets("CofA13").Visible = False
    Sheets("CofA14").Visible = False
    Sheets("CofA15").Visible = False
    Sheets("CofA16").Visible = False
    Sheets("CofA17").Visible = False
    Sheets("CofA18").Visible = False
    Sheets("CofA19").Visible = False
    Sheets("CofA20").Visible = False
ElseIf sWord = "5" Then
.....
EndIf

This is clearly cumbersome and could be polished up with a loop. I am not skilled enough ... yet ... to put this code together. Can someone give me a hand in doing this? The spark for this thread came from my code being too long when trying to introduce 40 sheets and the code not executing at all.

Thanks in advance

Evan

Private Sub Worksheet_Change(ByVal Target As Range)
Dim sWord As Integer
sWord = Sheets("Master").Range("B8").Value
  for j=1 to sWord
    sheetname="CofA" & j
    Sheets(sheetname).Visible = True
  next
  for i=j to ThisWorkbook.Sheets.Count
    sheetname="CofA" & i
    Sheets(sheetname).Visible = False
  next
end sub

Thanks patel45. It perfoms the function as intended, but it keeps giving me a "Run-time error '9': subscript out of range" message. The debugger goes to this lines: "Sheets(sheetname).Visible = False". Is this something on my end with the master spreadsheet or is this code related?

I think part of it may be that I have two spreadsheets titled "master" and "index". The code that states "for i=j to ThisWorkbook.Sheets.Count" would return a count 2 + higher than the CofA sheets that I want to hide.

I made a minor alteration to the code to account for these two pages. The completed code is below:

Private Sub Worksheet_Change(ByVal Target As Range)
Dim sWord As Integer
sWord = Sheets("Master").Range("B8").Value
    For j = 1 To sWord
        sheetname = "CofA" & j
        Sheets(sheetname).Visible = True
    Next
    For i = j To ThisWorkbook.Sheets.Count - 2
        sheetname = "CofA" & i
        Sheets(sheetname).Visible = False
    Next
End Sub

Again, thanks Patel45.