SYSTEM error no. -160

HI INFORMIX'ers table1 col1,col2 smallint, col3 text why I can't do something like this define rcd1 array[3] of record var1, var2 smallint end record, txt_var array[3] of text for each row in rcd1 I update txt_var variable, then after end input statment, I do insert rcd1 then update table1 set col3=txt_var[arr_crr] giving me error no -160.... any help...