I'm a quite new to VBA

With help from Gary''s Student in Excel Functions section i have written
the following macro to unhide cell based on the value of Cell $I$20 which has
a drop down list .
.................................................. .. VBA Code
..............................................
Private Sub Worksheet_Change(ByVal Target As Range)
If Intersect(Target, Range("I20")) Is Nothing Then
Exit Sub
End If

Rows("21:218").EntireRow.Hidden = True
unhide_um = Array("21:38", "21:56", "21:74", "21:92", "21:110", "21:128",
"21:146", "21:164", "21:182", "21:200", "21:218")
v = Range("I20").Value
If v = 0 Then
Exit Sub
End If
Rows(unhide_um(v - 1)).EntireRow.Hidden = False
End Sub
.................................................. .................................................. ........
what i require is to create a similar procedure in Cell $I$224 which will
unhide cell
"225:242", "225:260", "225:278", "225:296", "225:314", "225:332", "225:350",
"225:368" based on the value of Cell $I$224

I tried to create same worksheet Change event code but got a Run time error.
Any help will highly appreciated.