打印开始后，不能设置控件来源属性

[zxzy1981]

Private Sub 组页眉2_Format(Cancel As Integer, FormatCount As Integer)
Dim blm1 As String
Dim len1 As Integer
blm1 = [alltagname]
len1 = Len(blm1)
MsgBox (len1)
Select Case len1
Case 14
[blm].ControlSource = Mid([alltagname], 1, 11)
Case 13
[blm].ControlSource = Mid([alltagname], 1, 10)
Case 12
[blm].ControlSource = Mid([alltagname], 1, 9)
Case 11
[blm].ControlSource = Mid([alltagname], 1, 8)
Case 10
[blm].ControlSource = Mid([alltagname], 1, 7)
Case Else
[blm].ControlSource = Null
End Select
End Sub

运行报告说：“打印开始后，不能设置控件来源属性。”
可我还没打印啊，只是预览报表 DoCmd.OpenReport nowreport, acPreview
这问题怎么解决？？?请大家指教！

[zxzy1981]

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