在字段名称中使用变量-SQL Update语句

我是使用Access 2010的新手。我希望执行以下sql update语句，但是语法有问题。该表称为“预测”，用户将编辑和更新预测的数量。

问题-表的字段名称是2014_1、2014_2、2014_3 ...，表示存储在数组中的不同月份。我已经做了一些研究，我相信动态地做到这一点的方法是：

Dim sqlString As String
    sqlString = "UPDATE Forecasts " & _
    " SET Branch_Plant=" & Me.txtBranch_Plant & _
    ", Item_Number_Short='" & Me.txtItem_Number_Short & "'" & _
    ", Description='" & Me.txtDescription & "'" & _
    ", UOM='" & Me.txtUOM & "'" & _
    ", Estimated_Cost=" & Me.txtEstimated_Cost & _
    ", Requesting_Business_Unit='" & Me.txtRequesting_Business_Unit & "'" & _
    ", End_Customer='" & Me.txtEnd_Customer & "'" & _
    ", Project='" & Me.txtProject & "'" & _
    ", Forecasts." & "[" & arrMonthToDisplay(0) & "]" = " & Me.txtProjectedJanVolume " & _
    " WHERE ID =" & Me.txtID.Tag

    MsgBox ("This is the output: " & sqlString)
    CurrentDb.Execute sqlString 

在添加此行之前，一切正常

Forecasts." & "[" & arrMonthToDisplay(0) & "]" = " & Me.txtProjectedJanVolume

msgbx输出现在显示：“ False”。sqlString有什么问题？

请帮忙！非常感谢你。