表达式 ： 无法识别的标示符

表达式公式如下
=Sum(IIf( DateDiff("n",Fields!GetTime.Value,Fields!WorkDate.Value) < 0 ,1,0))/Count(Fields!时间.Value)
其中最后的"Value" 提示 无法识别的标示符
有的百分比算不出来

报表能运行最后一列的 公式有的算不出来

SQL如下：

SELECT ID AS 代码, Name AS 班车线, CONVERT(varchar(10), GetTime, 120) AS 日期,
CONVERT(varchar(5), GetTime, 108) AS 时间,
DATEPART(mi, GetTime) AS 分钟, GetTime, CONVERT(datetime, (CASE WHEN Name LIKE '工人%' THEN CONVERT(varchar(10), GetTime, 120) + ' 07:30' ELSE CONVERT(varchar(10), GetTime, 120) + ' 08:30' END)) AS WorkDate
FROM BC
WHERE (GetTime >= CONVERT(CHAR(10), DATEADD(dd, - DAY(GETDATE()) + 1, GETDATE()), 111)) AND (Name <> '工人东线') AND (Name <> ' 线路1') and Name<>'线路4'
ORDER BY GetTime