ciao Irshad,
assiming orders Northwind database example provided by Microsoft :

after creating a form like this, openinig it you will see all datas:

you achieve your task clicking on update command button whose event click code is :
Option Compare Database
Option Explicit
Private Sub cmdUpdate_Click()
With Me
.txtMessage = Null
If Len(.fromDate & vbNullString) = 0 Or Len(.toDate & vbNullString) = 0 Then
VBA.MsgBox prompt:="date criteria is wrong..!", _
Buttons:=vbCritical, _
Title:="Warning!!"
Exit Sub
End If
.lstOrders.Requery
If .lstOrders.ListCount > 0 Then
.txtMessage = "totRows:" & .lstOrders.ListCount & ", totValue:" & .lstOrders.Column(4, 0)
End If
End With
End Sub

and

sql code under listbox control is :
PARAMETERS [forms]![maschera11]![fromDate] DateTime, [forms]![maschera11]![toDate] DateTime;
SELECT Orders.OrderID, Orders.CustomerID, Orders.OrderDate, Orders.Freight,
(select sum(Freight) from orders where orderdate>=forms!maschera11!fromDate and orderdate<forms!maschera11!toDate+1 Or [forms]![maschera11]![fromDate] Is Null Or [forms]![maschera11]![toDate] Is Null) AS totFreight
FROM
Orders
WHERE
Orders.OrderDate>=[forms]![maschera11]![fromDate] And (Orders.OrderDate)<[forms]![maschera11]![toDate]+1
OR
[forms]![maschera11]![fromDate] Is Null OR [forms]![maschera11]![toDate] Is Null;
or like this :
PARAMETERS [forms]![maschera11]![fromDate] DateTime, [forms]![maschera11]![toDate] DateTime;
SELECT Orders.OrderID, Orders.CustomerID, Orders.OrderDate, Orders.Freight,
(select sum(Freight) from orders where orderdate>=forms!maschera11!fromDate and orderdate<forms!maschera11!toDate+1 ) AS totFreight
FROM
Orders
WHERE
Orders.OrderDate>=[forms]![maschera11]![fromDate] And (Orders.OrderDate)<[forms]![maschera11]![toDate]+1;
maybe the latter suits better your request since you are validating date values range.
in my opionion is an overKill looping through listobox item to sum each one to figure out the total value.
it's convenient add a calculated field on listbox sql predicate and show its content in txtMessage textbox control simply concatenating its value with listCount property.
HTH.
Ciao, Sandro.