function in a cell is not executing initially when i add data through userform

Question

Data is entered into cells using userfaorm, then this function

"=IFERROR(INDEX(PARTNO_BRAL,MATCH(0,COUNTIF($A$1:A3,PARTNO_BRAL),0)),"")"

should read data from cell that is entered by userform. But this function does nt work until i enter in the next row. Please suggest how i can fix this?

PARTNO_BRAL is a dynamic range.