电脑桌哪里买:VB编的学生登陆查询系统中遇到的问题，请赐教

Private Sub cmdfirst_Click()
On Error Resume Next
datscore.Recordset.MoveFirst

If datscore.Recordset.BOF Then datscore.Recordset.MoveFirst

End Sub

Private Sub cmdprevious_Click()
On Error Resume Next
Select Case cmdprevious.Caption
Case "上一条"
datscore.Recordset.MovePrevious

If datscore.Recordset.BOF Then datscore.Recordset.MoveFirst
Case "下一条"
datscore.Recordset.Update
datscore.Recordset.MoveLast
cmdfirst.Visible = True
cmdlast.Visible = True
cmdfirst.Caption = "首纪录"
cmdprevious.Caption = "上一条"
cmdnext.Caption = "下一条"
cmdlast.Caption = "尾纪录"
End Select
End Sub

Private Sub cmdnext_Click()
On Error Resume Next
Select Case cmdnext.Caption
Case "下一条"
datscore.Recordset.MoveNext
If datscore.Recordset.EOF Then datscore.Recordset.MoveLast
Case "取消"
datscore.UpdateControls
datscore.Recordset.MoveLast
cmdfirst.Visible = True
cmdlast.Visible = True
cmdprevious.Caption = "上一条"
cmdnext.Caption = "下一条"
End Select
End sub

Private Sub cmdlast_Click()
On Error Resume Next
datscore.Recordset.MoveLast
If datscore.Recordset.EOF Then datscore.Recordset.MoveLast

End Sub

主窗体，四个按钮的切换的问题如下：
1 当前纪录是首纪录时，在点击上一条，表格里什么都没有了，在点击下一条则不起作用
2 当前纪录是首末录时，在点击下一条，表格里什么都没有了，在点击上一条则不起作用