I need to show the textbox1 lengh as the use types data in it

In the event keypress of the textbox1, where user types data, has its value as a variable tag_number

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STORE ( LEN( tag_number)) TO field_lenght
thisform.text2.Value = field_lenght

thisform.refresh
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Textbox Test1 must show the lengh of the field

But something is wrong