Updating data from a main list after data has been split into smaller lists using VBA

Hello

I have a main list that has 15,000 entries in it. I need to split the list alphabetically which i have done using this VBA

Sub Split()

Sheet1.Activate
Sheet1.Range("A10:Z10").Select
Selection.Copy
Sheet2.Select
Range("A1").PasteSpecial
Sheet2.Range("C4").Select
Sheet1.Select
Application.CutCopyMode = False
Sheet1.Range("C15").Select
Sheet2.Select
Sheet1.Range("A10:Z18916").AdvancedFilter Action:=xlFilterCopy, CriteriaRange:=Sheet1.Range("AB10:AB11"), CopyToRange:=Sheet2.Range("A1:Z1"), Unique:=True

End Sub

This seems to work well but does take some time to process, around 5 minutes (A - Z)

But after I have split this data, when I update the master list I would like to have a macro which updates the sub lists.

How would this be possible? I was thinking I could just clear all of the data in the sub sheets and run the split macro again? Is there an easier way?

I have a limited understanding of what i am doing!

Cheers and thanks in advance,