I ran into this issue again today.  

Here is the solution.  

• On the screen SPLW add a after modification action to the new field  
• Validate the screen
• Then in the SPE add the following 

Subprog AM_YUDF(VALEUR)
Variable Integer VALEUR
    For I=0 To NBLIG-1 : [M]UPDFLG(I)=1 : Next I
End

• Compile the SPE
• Validate the Price list 

Hi Kyle, 

Maybe with this solution you coul doi it also the folloging:

#In Apres modif object action

$APRES_MODIF

    if COUZON="YUDF" :  [M]UPDFLG(I)=1 : endif

return

or 

# When the SPE field is changed

Subprog AM_YUDF(VALEUR)
Variable Integer VALEUR
  [M]UPDFLG(nolign-1)=1

End

Then you don't need to read all screen lines, each time you SPE filed is modified. We have price list eith more than 2.000 lines.

Regards

...sorry 

$APRES_MODIF

    if COUZON="YUDF" :  [M]UPDFLG(nolign-1)=1 : endif

return

Thank you Xavier, I had to adjust this a little.  Here is the final result.  

$APRES_MODIF
  If COUZON="YUDF"
    For I=0 To NBLIG-1 : [M]UPDFLG(I)=1 : Next I
  Endif
Return

mmmm, but then you need to read all screen lines!? 

Are you sure this not works:

$APRES_MODIF

    if COUZON="YUDF" :  [M]UPDFLG(nolign-1)=1 : endif

return

in theory nolign-1 will have the index of line you are positioned

I am positive.  It's actually the same behavior as some code in the SUB.