[class] Use of Custom Data Types in VBA

I am trying to create a custom data type in VBA for Excel. Let's call this data type "truck". Each truck has the following attributes:

NumberOfAxles (this is an integer)
AxleWeights (this is an array of doubles)
AxleSpacings (this is an array of doubles)

Can I create many instances of the data type "truck" (truck(1), truck(2)... etc), and read/write the attributes I listed above to that instance?

Example:

Truck(1).NumberOfAxles = 2
Truck(1).AxleWeights(1) = 15.0
Truck(1).AxleWeights(2) = 30.0
Truck(1).AxleSpacings(1) = 8.0

Truck(2).NumberOfAxles = 3
Truck(2).AxleWeights(1) = 8.0
Truck(2).AxleWeights(2) = 10.0
Truck(2).AxleWeights(3) = 12.0
Truck(2).AxleSpacings(1) = 20.0
Truck(2).AxleSpacings(2) = 4.0

and so on. The syntax above is most possibly wrong, I just wanted to demonstrate the structure I need to come up with.

All I am trying to write data to a data structure and call it as necessary such as

Truck(i).NumberOfAxles
Truck(i).AxleWeights(j)
Truck(i).AxleSpacings(j)

Thank you very much!

It looks like you want to define Truck as a Class with properties NumberOfAxles, AxleWeights & AxleSpacings.

This can be defined in a CLASS MODULE (here named clsTrucks)

Option Explicit

Private tID As String
Private tNumberOfAxles As Double
Private tAxleSpacings As Double


Public Property Get truckID() As String
    truckID = tID
End Property

Public Property Let truckID(value As String)
    tID = value
End Property

Public Property Get truckNumberOfAxles() As Double
    truckNumberOfAxles = tNumberOfAxles
End Property

Public Property Let truckNumberOfAxles(value As Double)
    tNumberOfAxles = value
End Property

Public Property Get truckAxleSpacings() As Double
    truckAxleSpacings = tAxleSpacings
End Property

Public Property Let truckAxleSpacings(value As Double)
    tAxleSpacings = value
End Property

then in a MODULE the following defines a new truck and it's properties and adds it to a collection of trucks and then retrieves the collection.

Option Explicit

Public TruckCollection As New Collection

Sub DefineNewTruck()
Dim tempTruck As clsTrucks
Dim i As Long

    'Add 5 trucks
    For i = 1 To 5
        Set tempTruck = New clsTrucks
        'Random data
        tempTruck.truckID = "Truck" & i
        tempTruck.truckAxleSpacings = 13.5 + i
        tempTruck.truckNumberOfAxles = 20.5 + i

        'tempTruck.truckID is the collection key
        TruckCollection.Add tempTruck, tempTruck.truckID
    Next i

    'retrieve 5 trucks
    For i = 1 To 5
        'retrieve by collection index
        Debug.Print TruckCollection(i).truckAxleSpacings
        'retrieve by key
        Debug.Print TruckCollection("Truck" & i).truckAxleSpacings

    Next i

End Sub

There are several ways of doing this so it really depends on how you intend to use the data as to whether an a class/collection is the best setup or arrays/dictionaries etc.