Jonathan,

Using the as-yet-to-be-documented record editing capabilities of 
SolrMarc I think you can you what you want.

create a file named    editor338.properties  in the same directory and 
SolrMarc.jar  that contains:
338=true
338_0=and(subfieldmatches("a", "online 
resource"),not(subfieldmatches("b","cr")))=>both(deletefield(),insertfield("338   
$aonline resource$bcr"))

and run SolrMarc as a filter:

cat   my_records.mrc  |
     java -Dsolrmarc.main.class="org.solrmarc.marc.MarcPrinter" 
-Dmarc.reader.remap=editor338.properties  -jar SolrMarc.jar  translate > 
my_edited_records.mrc


or you can even just add:

marc.reader.remap=editor338.properties

to your config.properties file, and the editing will be done as the 
records are read in for indexing.

-Bob


On 6/24/2014 12:39 PM, Jonathan Rochkind wrote:
> Hi code4libbers,
>
> I don't have much experience with MarcEdit, I'm hoping someone else 
> does, especially with creating automated MarcEdit "tasks", and can 
> advise:
>
> Would it be possible to create a MarcEdit task that:
>
> => IF there is 338 field with subfield $a "online resource", THEN 
> erase all existing subfield $b's in that field, and add a single 
> subfield $b "cr".
>
>
> We have records loaded from certain sources that have inconsistent 
> 338$a and $b, where the $a is the reliable one. I'm curious if I can 
> send records from these sources through a MarcEdit Task to correct 
> this known pattern of error.
>
> Anyone know if this is possible in a MarcEdit task? And if you could 
> supply some hints to a complete newbie to MarcEdit on how to do it, 
> that would be quite kind of you!
>
> Jonathan