[5分]请教一个代码意思

下面一段代码中有一句“ If ctl.ControlName =Split(strControls, ",")(i) And IsNull(ctl) Then”，这句意思是如果控件名找到且控件为空，这句不太好理解，请诸老师释疑。谢谢。

Function funIsNull(ByVal frmForm As Form, ByVal strControls As String) As Integer

      Dim ctl As Control

    A = UBound(Split(strControls, ","))

    For i = 0 To A

        For Each ctl In frmForm.Controls

            If ctl.ControlName =Split(strControls, ",")(i) And IsNull(ctl) Then

                MsgBox ctl.ControlName & "为空，请输入" & ctl.ControlName & "！", vbExclamation, "提示："

                ctl.SetFocus

                funIsNull = True

                Exit Function

            End If

        Next ctl

    Next i