Validate data Using Table maintence generator

Question

Hi Gurus,
I need to validate a first 2 char of a field(say fld1-char 3) of a table(say TAB1) against a field (say fld2 -char 2) of another table Tab2.
In the maintence screen PAI ,I am using 'Field & Select' keyword to validate the fld1 against fld2.
Code:
FIELD ZZMAL_HR-DAT00 SELECT   *
            FROM  t548y
            WHERE datar = ZZMAL_HR-dat00+0(2)
            INTO  DAT00
            WHENEVER NOT FOUND SEND ERRORMESSAGE 001.
But on data insertion screen :
a) on directly entering invalid value to the screen field & pressing save button,it saves it.
b)on taking F4 prompt & selecting the value,it is not copied to the screen field.
Can any body explain how to solve it?
if I am directly hard coding like:
field ZZMAL_HR-DAT00 values ('Z1','Z2','Z3','Z4').
this works fine!
All the code is written in PAI directly.
Since I am not able to create module(unavailability of acess key),i am not able to even use hard coded break points(it becomes  a syntax-error) & also call to 'F4- ..' fn etc can not be made in POV, as Call keyword  is only allowed in PAI & PBO!(when coding directly in Flow logic without any module).......
Awaiting guidance........
regards,
Gaurav

Answer 1

Before you hit the SAVE button, have you tried putting /h in the command box and hitting ENTER to invoke the debugger?  It may be somewhat difficult to work through the SAP generated code.  Try and determine if your code is getting executed.
I also see from the documentation on this feature, that the syntax restrictions for SELECT are different from SELECT in ABAP code.  Try coding
datar = ZZMAL_HR-dat00
without the offset info and see if that makes a difference.  Also try leaving out the INTO clause since you do not really need the data.