Split Workbook Into Multiple Workbooks

I'm attempting to take a Workbook that contains 1000 Worksheets and split it into 2 separate WB's of 500 WS's each ... basically half it. This could also apply to a WB that contains less than 1000 WS's, but it is highly unlikely it will ever contain more than 1000 WS's.

I'd like each new WB created to be saved in the original path with the original filename followed by a "1", "2", "3" or "a", "b", "c", etc. For example:
Original Filename = ImpactAnalysis.xls
New Filename 1 = ImpactAnalysis (1).xls or ImpactAnalysis (a).xls
New Filename 2 = ImpactAnalysis (2).xls or ImpactAnalysis (b).xls

I've located 2 modules in the forum that are a good start, but each creates a separate WB for each WS, which is a bit cumbersome with up to 1000 WS's in the original WB.


Sub splittest()
Dim sht As Worksheet
Dim w As Worksheet
Application. ScreenUpdating = False
Application.DisplayAlerts = False
For Each sht In Worksheets
Set neww = Workbooks.Add
sht.Copy neww.Worksheets(1)
With neww .....................