If form field has text display "KG" in another form field

All,

Is there any way to make it so that if a field called "10 MARKED WEIGHT OF LOTRow1" has numerical data in it that "KG" is entered into "10 MARKED WEIGHT OF LOTRow1a" and if there is no numerical weight entered in "10 MARKED WEIGHT OF LOTRow1" that "10 MARKED WEIGHT OF LOTRow1a" is left blank. Any help is appreciated. I'm editing this on Mac for use on Windows PC.

Thanks

-J