SQL Failing To Pick Up List Box Value

Hi all

I have a form which is used for entering holiday requests.

It has fields such as name, type of holiday, date from and date to but it also has a list box value. This list box contains the number of days between the date from and date to and exludes weekends and bankholidays using data from a table. The data from the form is inserted into a table using an sql string when the submit button is pressed. The problem I have is that the sql does not pick up the number of days from the list box unless I click on the list box before I click on submit. It is almost as if the value is in the list box but it is simply not recognised by the sql unless I select the list box using the mouse. I have tried to select the list box using code when the submit button is pressed but to no avail. Does anyone have any ideas how I can over come this or perhaps how to physically select the list box so it is highlighted when the submit button is pressed??

Thanks all

Gareth