My macro freezes after an undefined amount of iterations - vba

Question

I have a macro that checks if some names on column Q appear on column A (which is ordered alphabetically) and prints them out on column S if they do. However, every time I run it it freezes after an undefined amount of iterations (never on the same amount of iterations) so it's really hard to know what's going on. If I run it with a breaking point and press F5 for each iteration it doesn't freeze, the thing is I have thousands of names to compare and I really don't want to press F5 that many times.
Here's my code:
Sub test()
Range("Q2").Select
analizados = 0
falsos = 0
Do Until IsEmpty(ActiveCell)
id1 = ActiveCell.Value
primera = Left(id1, 1)
Range("A2").Select
Do While Not ActiveCell.Value Like "" & primera & "*"
ActiveCell.Offset(1, 0).Select
Loop
Do While ActiveCell.Value Like "" & primera & "*"
If id1 = ActiveCell.Value Then
Range("S2").Select
ActiveCell.Offset(falsos, 0).Select
ActiveCell.Value = id1
falsos = falsos + 1
Exit Do
End If
ActiveCell.Offset(1, 0).Select
Loop
analizados = analizados + 1
Range("Q2").Select
ActiveCell.Offset(analizados, 0).Select
Loop
End Sub
Thank you

Answer 1

As you noticed, it's not actually frozen. It's just that Excel can't keep up with updating the screen as fast as you're bombarding it with "something has changed on the active sheet" events, and at one point it gives up and lets the macro complete without bothering with refreshing - at least that's how I understand it (might not be exactly what's going on though).
Try this:
Sub Test()
On Error GoTo ErrHandler
Application.ScreenUpdating = False
'...
'(rest of your code)
'...
CleanExit:
Application.ScreenUpdating = True
Exit Sub
ErrHandler:
MsgBox Err.Description
Resume CleanExit
End Sub
Basically you tell Excel to not even bother with repainting itself until you're done: this should greatly speed up your loops.
You may want to combine this with different settings for Application.Calculation and Application.Cursor, too; and for a better UX you could use the status bar to tell the user to wait a little:
Sub Test()
On Error GoTo ErrHandler
Application.StatusBar = "Please wait..."
Application.ScreenUpdating = False
'...
'...
CleanExit:
Application.StatusBar = False
Application.ScreenUpdating = True
Exit Sub