测试变量是否为空值，空值的含义包括：变量不存在/为空，对象为Nothing，0，空数组，字符串为空
Function IsBlank(ByRef Var)
IsBlank = False
Select Case True
Case IsObject(Var)
If Var Is Nothing Then IsBlank = True
Case IsEmpty(Var), IsNull(Var)
IsBlank = True
Case IsArray(Var)
If UBound(Var) = 0 Then IsBlank = True
Case IsNumeric(Var)
If (Var = 0) Then IsBlank = True
Case Else
If Trim(Var) = "" Then IsBlank = True
End Select
End Function