We are often faced with the task of knowing the lengths of certain elements in a drawing.
Here is a simple example using VBA that adds up the length of all existing arcs in the active model sheets.

Sub arcLength()
Dim sum As Double
sum = 0
Dim ee As ElementEnumerator
Dim Sc As New ElementScanCriteria
Sc.ExcludeAllTypes
Sc.IncludeType msdElementTypeArc
Set ee = ActiveModelReference.GraphicalElementCache.Scan(Sc)
Do While ee.MoveNext
 sum = sum + ee.Current.AsArcElement.Length
Loop
If sum = 0 Then
    MsgBox "No Sheets Found", vbOKOnly
Else
    MsgBox "Total length of all sheets: " & sum, vbOKOnly
    Debug.Print sum
End If
End Sub

In the above example, the active arcs' model is read, and then the lengths of the individual active arcs are read and added together.
The result is displayed in a dialog box, or if no sheet has been found that is specified.