OnTime Method [Excel 2003 VBA Language Reference]
Schedules a procedure to be run at a specified time in the future (either at a specific time of day or after a specific amount of time has passed).
expression .OnTime(EarliestTime, Procedure, LatestTime, Schedule)
expression Required. An expression that returns an Application object.
EarliestTime Required Variant. The time when you want this procedure to be run.
Procedure Required String. The name of the procedure to be run.
LatestTime Optional Variant. The latest time at which the procedure can be run. For example, if LatestTime is set to EarliestTime + 30 and Microsoft Excel is not in Ready, Copy, Cut, or Find mode at EarliestTime because another procedure is running, Microsoft Excel will wait 30 seconds for the first procedure to complete. If Microsoft Excel is not in Ready mode within 30 seconds, the procedure won't be run. If this argument is omitted, Microsoft Excel will wait until the procedure can be run.
Schedule Optional Variant. True to schedule a new OnTime procedure. False to clear a previously set procedure. The default value is True.
Now + TimeValue(time) to schedule something to be run when a specific amount of time (counting from now) has elapsed. Use
TimeValue(time) to schedule something to be run a specific time.
This example runs my_Procedure 15 seconds from now.
Application.OnTime Now + TimeValue("00:00:15"), "my_Procedure"
This example runs my_Procedure at 5 P.M.
Application.OnTime TimeValue("17:00:00"), "my_Procedure"
This example cancels the OnTime setting from the previous example.
Application.OnTime EarliestTime:=TimeValue("17:00:00"), _ Procedure:="my_Procedure", Schedule:=False