That depends. It would help a lot if you provided specific details about what it is you want to accomplish.
Okey, thank you!
Then I have button" btnVro". And when user push the button I would like to call/run this "On Blur" event in this text field "fldLahpvm" witch then check that this text field input is right formula.
To validate user input you should use the Validate event of the field. That
is what it was meant for.
And why would you need to validate the value again, if you already did it
when the user entered the value originally?