Lets look at it like this. If the user is able to deselect they are in essence making all values available in any object that references to that field as a dimension. In QlikView, it would be the same as selecting all values.
However, if the chart or object using that value has a calculate conditional for when getselectedcount is one, then I can understand where this would be useful.
My suggestion as I know no other way to clear the selection when only 1 selection is enabled is to do one of the following
1) Create an input box with a concat function to list all values in a drop down. Forcing the user to select a value or blank
2) Min or MaxString can be used to force QlikView to select one value even though the list box has multiple values. The value that will be used in the object can be represented by a text box indicating which value has taken precedence
3) If your list box contains only a few options, then maybe FieldValue and FieldIndex can be used with a forced element number of 1
Hope the above is useful to you in any way
Byron Van Wyk
You can follow the steps below:
1. Go to Document Properties/ field trigger
2. On Select-->Select in Field
3. Time Period
4, in the expression Type:
In this way user will be able to select/ deselect values but not multiselect. Instead of Maxstring minstring function can also be used.
Hope it helps..