My Program Isn't Selected The Right Item That Click On - Allows A User To View A List Of Foods In A Combo Box

I am creating a program that allows a user to view a list of foods in a combo box, add that food unto a list box, and adds all of the calories of that food together. When the user highlights their select food, the program automatically shows the amount of calories for that particular food in a text box. The program is getting the food and calorie information from an access database. I managed to get all of the food calories to add up properly, however, I ran into a problem. Sometimes, well, most of the time, when I select certain foods from the combo box, the program automatically reselects another random food, usually a food that begins with either an A, B, or C. Also, the other random food that the program chooses usually has the same amount of calories as the food I originally wanted to choose. I have over 6,000 items in the database. I don't understand why this is happening. This is what my code looks like for the button that adds each food to the list box:

Private Sub Button4_Click(sender As System.Object, e As System.EventArgs) Handles Button4.Click
Foods_Selected.Items.Add(ComboBox1.Text)

Static i As Single

[CODE]...

And this is what my code looks like for the button that adds all of the foods together:

Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click

Dim x As Single
Dim TotalCalories As Single

[CODE]...

I have no idea what to try. It's like the program just skips over random foods, even though all of the information for them is in the database.