a=1: t = time 执行时为何提示“变量未定义”？

WANGL2

Dim t As Date
Dim a
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
x = Target.Row
y = Target.Column
If (3 < x And x < 9) And (y > 7 And y < 13) Then
Cells.Interior.ColorIndex = xlNone
Target.Interior.ColorIndex = 41
    If Target = 1 Then
        a = 1: t = time
    End If
    If Target = 25 And a = 1 Then
        b = time - t
        s = Second(b)
        m = Minute(b)
        MsgBox "用时" & m & "分" & s & "秒", , "时间提示"
        a = 0
    End If
End If
End Sub

这儿有肥猫

加一句，dim t

WANGL2

不报错了，但计时不准。谢谢！

这儿有肥猫

?哪里不准？