Sub gen()
Dim arr(1 To 20) As Integer, i As Integer, ir As Integer, ich As Integer
Randomize
Do
    For i = 1 To 19
    arr(i) = Fix(90 * Rnd + 10)
    ir = ir + arr(i)
    Next
    ich = 1000 - ir
    If ich < 10 Or ich > 100 Then
        Erase arr
        ich = 0
        ir = 0
    Else
        arr(20) = ich
        Exit Do
    End If
    
Loop
For i = 1 To 20
    Cells(i, 8).Value = arr(i)
Next
End Sub