Not that I can think of which is foolproof. In theory you can set traps in KeyPress, but it would be a lot of work.
Why not have two textboxes very close, one with 04_ which is readonly, and the other with only the billno?

>hi,
>thank you so much,it works.
>any way to let 04_ at mytext all the time at myform.
>just can i insert billno as 0003 at my text.
>
>thanks.
>best regards.
>m.qasem
>
>>

>>inyearofbill=2000+VAL(LEFT(thisform.text1.Value,2))
>>inbillno=INT(VAL(SUBSTR(thisform.text1.value,4)))
>>IF USED('billinfo')
>>  SELECT Billinfo
>>ELSE
>>  SELECT 0
>>  USE billinfo AGAIN && Billinfo may be used in another work area with another alias, so use AGAIN to be safe
>>ENDIF
>>LOCATE for YEAR(billdate)=inyearofbill AND billno=inbillno
>>IF FOUND()
>>  thisform.text2.value=name
>>  .
>>  .
>>  .
>>ELSE
>>  =MESSAGEBOX("not found")
>>endif
>>

>>>hi,
>>>thank you very much,it works
>>>i need to change this code with locate or scan as under
>>>

>>>
>>>inyearofbill=2000+VAL(LEFT(thisform.text1.Value,2))
>>>inbillno=INT(VAL(SUBSTR(thisform.text1.value,4)))
>>>SELECT * from billinfo WHERE YEAR(billdate)=inyearofbill AND billno=inbillno INTO CURSOR curbilldata
>>>************
>>>LOCATE for YEAR(billdate)=inyearofbill AND billno=inbillno
>>>IF FOUND()
>>>thisform.text2.value=name
>>>.
>>>.
>>>.
>>>ELSE
>>>=MESSAGEBOX("not found")
>>>endif
>>>********************
>>>

>>>
>>>thanks.
>>>m.qasem
>>>
>>>>

>>>>INSERT  INTO  billinfo(billno,billdate) VALUES (val(right(thisform.text1.Value,4)),DATE())
>>>>

>>>>Remember that the value showed in thisform.text1.Value, 04-0001, is ONLY ment to show nicely, it is not the actual billno.
>>>>
>>>>>hi,
>>>>>thank you very much,it works
>>>>>i try to insert myvalue as under ,but i get error messag(data type mismatch)
>>>>>

>>>>>INSERT  INTO  billinfo(billno,billdate) VALUES (thisform.text1.Value,DATE())
>>>>>

>>>>>thanks.
>>>>>m.qasem
>>>>>
>>>>>>Try this.
>>>>>>
>>>>>>thisform.text1.value=RIGHT(STR(YEAR(DATE()),4),2) + '_'+RIGHT(STR(10000+(billinfo.billno+1),5),4)