Database engine can not lock table

The following code produces the error: The database engine could not lock
table 'printout' because it is already in use by another person or process.

Any ideas why I am getting this error and how I can fix it? Thanks!

Dim tblName As TableDef
Dim strFieldName As String
Dim intFieldType As Integer
Dim lngAttributes As Long
Dim intMaxLength As Double
Dim tmpNewField As Field

Set tblName = dbMyDB.TableDefs("printout")

strFieldName = "ID"
intFieldType = dbLong
lngAttributes = dbAutoIncrField
intMaxLength = 100


Set tmpNewField = tblName.CreateField(strFieldName, intFieldType,
intMaxLength)'

tmpNewField.Attributes = lngAttributes

tblName.Fields.Append tmpNewField