Hi

in general for Real tags you should have a hysteresis implemented - so small changes (noise) are ignored.

PSEUDOCODE

if (Abs(Tag-Old_Tag)>=Hysteresis) {
    Tag_Changed=True;
    Old_Tag=Tag;
}

STL

L Tag
L Old_Tag
-R
ABS
L Hysteresis
>R
JCN SKIP
L Tag
T OLD_TAG // OLD_TAG must be a STAT / MD / DBxxx.DBDyyy
S Tag_Changed // Changed must be STAT/Mx.y / DBxxx.DBXyyy.z
SKIP: (...) continue with code

Assume Tag_Changed is cleared in part of program where you use it.

this approach will eliminate reaction to noise or even rounding errors when tag is a result of calculation.