帮我解释一下下面程序的含义（VB的并每行大概意思帮助解释一下）谢谢

Private Sub Command1_Click(Index As Integer)
Dim i, j As Long
Dim a1, a2, a3, a4, a5, c As Long
If Index = 0 Then
For i = 0 To 10
For j = 0 To 18
BLK.MaskPos(i * 19 + j).Y = 32700 - i * 4000
Next
Next
Else
a1 = 12000
a2 = 9000
a3 = -6050
a4 = -8800 - 250
a5 = -24000
c = 1750

For i = 0 To 10
BLK.MaskPos(i * 19).X = a1
Next

For i = 1 To 8
For j = 0 To 10
BLK.MaskPos(j * 19 + i).X = a2 - (i - 1) * c
Next
Next

For i = 0 To 10
BLK.MaskPos(i * 19 + 9).X = a3
Next

For i = 10 To 17
For j = 0 To 10
BLK.MaskPos(j * 19 + i).X = a4 - (i - 10) * c
Next
Next

For i = 0 To 10
BLK.MaskPos(i * 19 + 18).X = a5
Next

End If

End Sub