ByVal or ByRef - Arrays

When you declare a variable with an Array data type it can only be passed in using ByRef.
The Array data type is a Value data type.

ByRef

Passing an Array into a subroutine using ByRef allows the original variable to be changed.

Public Sub Passing_Arrays() 
   Dim myArray(3) As Integer 
   myArray(0) = 1 
   myArray(1) = 2 
   myArray(2) = 3 
   myArray(3) = 4 
   Debug.Print myArray(2)    '3  

   Call ByReference(myArray)   'must use Call  
   Debug.Print myArray(2)    '8  
End Sub 

'must be ByRef
Public Sub ByReference(ByRef myArray2() As Integer) 
   'this changes the original
   myArray2(2) = 8 
   
   'this changes the original
   myArray2(2) = 8 
End Sub 

ByVal

Passing an Array into a subroutine using ByVal is not possible.
If you try and declare an array parameter that is passed ByVal you will get a compile error

Public Sub ByValue(ByVal myArray2() As Integer) 
End Sub 

SS - array argument must be byref