I have an SQL table that contains 4 columns

1) ID
2) EquipmentID
3) Date
4) Hours e.g. 10000

I have an SSRS report that displays the contents of this table

A from and to date parameter is used to select a date range of records

The table is grouped by equipment

In the equipment group I have added a row below with the following expression in the hours column

Last(Fields!Hours.Value) - First(Fields!Hours.Value) = "Total actual hours used"
e.g. 10000 - 9500 = 500

This is does not return the correct "Total actual hours used"

The expression is incorrect

It should actaully be...

Last(Fields!Hours.Value) - PREVIOUS(First(Fields!Hours.Value)) = "Total actual hours used"
e.g. 10000 - 9450 = 550

My issue is how can I get PREVIOUS(First(Fields!Hours.Value)?

By selecting the parameter date range I do not retrieve PREVIOUS(First(Fields!Hours.Value)

Thanks!