>I have a very large table over 300,000 records
>
>I am using locate for command
>I can not use seek because I have conditions seek does not fulfill
>
>The first time a use the command locate,it is very slow
>
>The second time and then, locate is very fast
>
>The command is in a button of a form and table in date environment
>If I close the form, the first time I use locate it is slow again
>
>Is there any explanation for it ?

Are you by any chance starting out with a GO TOP command? That is not optimizable and will be very slow. Instead, issue LOCATE with no parameters. That will put the record pointer at the first record.