i want code help for the my form in sap b1?

i have created the form in which, i take the value from the user in textbox1

and in text box 2 and textbox 3  i want to fetch the value of cardcode and CardName form the table OPDN where the DocNum/Doc Entry is equal value entered in textbox 1

and in matrix want to fetch the value of itemcode, and quantity from the table PDN1 where the DocNum/Doc Entry is equal value entered in textbox 1

plz help me

textbox 2,textbox 3 and matrix in not editable.