Do autonumber in forms

You have to do it with code. You would need to lock the cell
and have the value populated via macro

Yeah I kind of suspected that after I posted the message, I noticed your name. I guess you were the one who was looking for changing the text of the button.

The answer to this one is simple and not so simple. For that one has to look at the form. Here is the basic idea

To lock the cell.
First select all the cell and right click and go to format
There is option for protection. Uncheck the box.
Now right click the cell where you want that value to be and again go to format and enable the lock.
Now the lock is not operational till the sheet is lock. You need to go o Review tab and there is a protect worksheet option.

Now this all prevents a user to type in the value there.


Now to auto increment the lock cell. For that you have to change the code for the button

Write a sub like this

Sub incrementValue()
Dim currentValue As Variant

    'Assuming that the locked value is on sheet1 and cell C1
    currentValue = Sheets("Sheet1").Cell(1, "C").Value
    
    ' if the cell is blank then, value is 0
    If currentValue = "" Then currentValue = 0
    
    ' a safety issue. In case the value in cell c1 was not numeric then we dont want to mess up
    If (IsNumeric(currentValue)) Then
        currentValue = currentValue + 1
    
        Sheets("Sheet1").Cell(1, "C").Value = Right("000" & currentValue, 3)
    
    End If

End If

Now in the code for button, add one more line

Call  incrementValue

It is code for the form.