I have the following three rows
CREDITRow1 has the following custom validation script: this.getField("DEBITRow1").readonly = (Number(event.value)>0);
If I enter a value in DEBITRow1 it correctly make CREDITRow1 read only, but when I go to tab from DEBITRow1 to Line DescriptionRow1 it tabs back to the top of the page and the first field. How can I correct this?
Check the tab order, and make sure that the Line Description field comes after the Credit field in it.
I just tried it in a sample file I created and it worked fine. Could you share your file with us (via Dropbox, Google Drive, etc.)?