I have a rather large model that works fine with the exception of one part (See Figure 1). What I can't seem to figure out is how to select all "NULLs" (for example) in a field and then perform a calculation on the NULLs selected, then move on to the next field listed in the "Field" variable. It just runs through the first Field then stops. Any ideas would be helpful.
The Calculate Field tool works for only one field at a time. You'll need to connect another Calculate Field at the end of that model.
Repeat for every field you need to calculate.