Sub Random20()
    Randomize 'Initialize Random number seed
    Dim MyRows() As Integer    ' Declare dynamic array.
    Dim numRows, percRows, nxtRow, nxtRnd, chkRnd, copyRow As Integer
    'Determine Number of Rows in Sheet1 Column A
    numRows = ThisWorkbook.Sheets(1).Range("A" & Rows.Count).End(xlUp).Row
    'Get 20% of that number
    percRows = 225
    'Allocate elements in Array
    ReDim MyRows(percRows)
    'Create Random numbers and fill array
    For nxtRow = 1 To percRows
getNew:
        'Generate Random number
        nxtRnd = Int((numRows) * Rnd + 1)
        'Loop through array, checking for Duplicates
        For chkRnd = 1 To nxtRow
            'Get new number if Duplicate is found
            If MyRows(chkRnd) = nxtRnd Then GoTo getNew
                Next
            'Add element if Random number is unique
            MyRows(nxtRow) = nxtRnd
            Next
        'Loop through Array, copying rows to Sheet2
        For copyRow = 1 To percRows
            ThisWorkbook.Sheets(1).Rows(MyRows(copyRow)).EntireRow.Copy _
        Destination:=ThisWorkbook.Sheets(2).Cells(copyRow, 1)
    Next
End Sub