Carolina Minte-Vera has developed ADMB syntax files for the Crimson Editor. The Crimson Editor editor has many characteristics such as syntax highlighting and parenthesis matching.
You can download the Crimson Editor for free.
Set up the ADMB syntax file from the “syntax type” item in the “Document” menu. Choose customize. Choose an empty slot to define new language. Enter “ADMB” in the description box, choose “ADMB.SPC” in the Lang. spec. box, choose “ADMB.KEY” in the Keywords box.
Download the extension.tpl file and save it in the folder C:\Program Files\Crimson Editor\link overwriting the existing file. This will allow the Crimson Editor to automatically identify a ADMB tpl file.