update form instantly

[vivou]

hi!
i have a form, with some buttons grouped in opion group: a,b,c,d,e,f,....,z

and in the form i have edits with people data.

i want the following:
when i press a button, i will refresh the form with the data people who their name begin by the pressed letter.
+ refresh instantly.

i try :
Dim strFilter As String

Select Case Me.frSelectLetter

Case 1
strFilter = "Nameoftable.FieldName Like 'A*' "

Case 2
strFilter = "Nameoftable.FieldName Like 'B*' "

'etc etc - through the alphabet

End Select

Me.Filter = strFilter
Me.FilterOn = True

end sub

but there is still a major problem, after go out of the case sentence, on the "Me.Filter = strFilter"
i get:
run time error 7752
cant apply the filter because all the records are locked"

why that?? i did not locked anything!

and in the run form i can see:
in the navigation control, 1 of 6 (filtered)

how can i do that???