VB & VBA in a Nutshell: The Language

Lock Statement

Syntax

Lock [#]filenumber[, recordrange]

filenumber

Use: Required

Data Type: Integer

Any valid file number.

recordrange

Use: Optional

Data Type: Long

A range of records.

The syntax for the recordrange argument is:

recnumber | [start] To end

recnumber

Use: Required

Data Type: Long

The record or byte number at which to commence the lock.

start

Use: Optional

Data Type: Long

The first record or byte number to lock.

end

Use: Required

Data Type: Long

The last record or byte number to lock.

Description

Use the Lock statement in situations where multiple programs or more than one instance of your program may need read and write access to the same data file. The Lock statement prevents another process from accessing a record, a section, or the whole file until it's unlocked by the Unlock statement.

Rules at a Glance

• recnumber is interpreted as a record number in the case of random files and a byte number in the case of binary files. Records and bytes in a file are always numbered sequentially from 1 onward.

• To lock a particular record, specify its record number, and only that record is locked.

• Use the Lock statement, omitting recnumber, to lock the whole file.

• The Lock statement locks an entire file opened in input or output (sequential) mode, regardless of the recordrangeargument.

• If you omit the start argument in the recnumber syntax, Lock locks all records from the start of the file to record or byte number end.

• Attempting to access a locked file or portion of a file ...