一个窗口中有绑定一个表并有4个panel

我在窗口中代表ID的textbox中设置了一个valuechange，如下。

目的是，当我选择表中不同行时，根据不同的situation，来决定4个panel的颜色。

课时在这个form载入时弹出错误，应该是在载入过程中，某对象来不及载入触发事件导致。

请问如何解决。谢谢！

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错误所在事件：窗口,submit-1,TextBox1,ValueChanged
详细错误信息：
未将对象引用设置到对象的实例。

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Dim tb As Table = Tables("Data_Basic")
Dim r As Row = tb.Current
Dim adrs As String = r("AttachedImage")
Dim adrs2 As String = r("AttachedImageAfter")
Dim Fm As winform.Form = Forms("submit-1")
Dim pic As winform.picturebox = fm.controls("PictureBox1")
Dim pic2 As winform.picturebox = fm.controls("PictureBox2")

If adrs = "" Then
pic.ImageFile = projectpath & "\\images\\NULLIMAGE.jpg"
Else
pic.ImageFile = adrs
End If

\'载入图片
If adrs2 = "" Then
pic2.ImageFile = projectpath & "\\images\\NULLIMAGE.jpg"
Else
pic2.ImageFile = adrs2
End If

\'如果为空则退出
If fm.controls("textbox1").text = "" Or fm.controls("textbox25").text = ""
Exit Sub
End If

\'显示状态
Dim s1 As WinForm.Panel = fm.Controls("Panel1")
Dim s2 As WinForm.Panel = fm.Controls("Panel2")
Dim s3 As WinForm.Panel = fm.Controls("Panel3")
Dim s4 As WinForm.Panel = fm.Controls("Panel4")
s1.BackColor = Color.lime
s2.BackColor = Color.lime
s3.BackColor = Color.lime
s4.BackColor = Color.lime

If r("situation") = "提交" Then
s1.BackColor = Color.whitesmoke
s2.BackColor = Color.whitesmoke
s3.BackColor = Color.whitesmoke
s4.BackColor = Color.whitesmoke
Else If r("situation") = "审核" Then
s2.BackColor = Color.whitesmoke
s3.BackColor = Color.whitesmoke
s4.BackColor = Color.whitesmoke
Else If r("situation") = "接手" Then
s2.BackColor = Color.whitesmoke
s3.BackColor = Color.whitesmoke
s4.BackColor = Color.whitesmoke
Else If r("situation") = "返工" Then
s2.BackColor = Color.whitesmoke
s3.BackColor = Color.whitesmoke
s4.BackColor = Color.whitesmoke
Else If r("situation") = "完成" Then
s3.BackColor = Color.whitesmoke
s4.BackColor = Color.whitesmoke
Else If r("situation") = "验收" Then
s4.BackColor = Color.whitesmoke
End If

知道原因了，一定要写在dim r的下面，否则代码第三行和第四行都会出错。