yes/no fields

i have this peice of coding, but i am getting an error
rs1.Fields("Available") = "True"
for some reason i get an error
' object or provider is not capable of of performing requested operation.
what am i doing wrong
the fields available is a true/false data type

can some one please please tell me what i am doing wrong

Dim varBookmark As Variant
Dim rs1 As Recordset
Set rs1 = New Recordset
Dim string1 As String
Dim string2 As String
string1 = Left(textpass, 5)
string2 = Right(textpass, 3)

rs1.ActiveConnection = "Provider=Microsoft." & "Jet.OLEDB.4.0;Data Source=C:\" & "My Documents\VStore97.mdb;" & "Persist Security Info=False"

rs1.Open "select * from Copies where Video = " & string1 & " and SerialNo = " & string2 & ";"

If rs1.EOF = True Then
Findcopyvideo = False
rs1.Bookmark = varBookmark
Else
If rs1.Fields("Available") = False Then
copyid = rs1.Fields("ID")
rs1.Fields("Available") = "True"
rs1.Update
Else
MsgBox "This is movie is already Checked out"
End If