Quicksort implementation in VBScript / VBA

QuickSort.vbs

Sub QuickSort(ByRef ThisArray)
	'Sort an array alphabetically
	
	Dim LowerBound, UpperBound
	
	LowerBound = LBound(ThisArray) 
	UpperBound = UBound(ThisArray) 
	
	QuickSortRecursive ThisArray, LowerBound, UpperBound
End Sub

Sub QuickSortRecursive(ByRef ThisArray, ByVal LowerBound, ByVal UpperBound)
	'Approximate implementation of https://en.wikipedia.org/wiki/Quicksort
	
	Dim PivotValue, LowerSwap, UpperSwap, TempItem
	
	'Zero or 1 item to sort
	If UpperBound - LowerBound < 1 Then Exit Sub
	
	'Only 2 items to sort
	If UpperBound - LowerBound = 1 Then
		If ThisArray(LowerBound) > ThisArray(UpperBound) Then
			TempItem = ThisArray(LowerBound)
			ThisArray(LowerBound) = ThisArray(UpperBound)
			ThisArray(UpperBound) = TempItem
		End If
		Exit Sub
	End If
	
	'3 or more items to sort
	PivotValue = ThisArray(Int((LowerBound + UpperBound) / 2))
	ThisArray(Int((LowerBound + UpperBound) / 2)) = ThisArray(LowerBound)
	
	LowerSwap = LowerBound + 1
	UpperSwap = UpperBound
	
	Do
		'Find the right LowerSwap
		While LowerSwap < UpperSwap And ThisArray(LowerSwap) <= PivotValue
			LowerSwap = LowerSwap + 1
		Wend
		
		'Find the right UpperSwap
		While LowerBound < UpperSwap And ThisArray(UpperSwap) > PivotValue
			UpperSwap = UpperSwap - 1
		Wend
		
		'Swap values if LowerSwap is less than UpperSwap
		If LowerSwap < UpperSwap then
			TempItem = ThisArray(LowerSwap)
			ThisArray(LowerSwap) = ThisArray(UpperSwap)
			ThisArray(UpperSwap) = TempItem
		End If
	Loop While LowerSwap < UpperSwap
	
	ThisArray(LowerBound) = ThisArray(UpperSwap)
	ThisArray(UpperSwap) = PivotValue
	
	'Recursively call function
	
	'2 or more items in first section
	If LowerBound < (UpperSwap - 1) Then QuickSortRecursive ThisArray, LowerBound, UpperSwap - 1
	
	'2 or more items in second section
	If UpperSwap + 1 < UpperBound Then QuickSortRecursive ThisArray, UpperSwap + 1, UpperBound
	
End Sub