hi,
thank's again for replay.
i creat new form ,i put 3 textbox at it,
i write my code like

on textbox3.refresh
this.value=ttoc(thisform.text1.value-thisform.text2.value,2)

on textbox6.refresh
this.value=ttoc(thisform.text4.value-thisform.text5.value,2)

on textbox12.refresh
sum of thisform.text3.value+thisform.text6.value,2)
this.value=ttoc(sumvalue,2)

i don't know where is the error
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i get error message
functin argument value,type or count is invalid