An array in a structure is declared with an initial size. You cannot initialize any structure element, and declaring an array size is one form of initialization.
Error ID: BC31043
To correct this error
Define the array in your structure as dynamic (no initial size).
If you require a certain size of array, you can redimension a dynamic array with a ReDim Statement when your code is running. The following example illustrates this.
Structure demoStruct Public demoArray() As Integer End Structure Sub useStruct() Dim struct As demoStruct ReDim struct.demoArray(9) Struct.demoArray(2) = 777 End Sub