Here is a bizarre update. My spreadsheet is extremely large (~75,000 rows). I am using Excel 2007, so that should be okay, right? My data in the first few hundred rows is very sketchy, so I was updating the formula in the bottom rows to then copy upward. I went to copy a portion for this post, and rather than copy rows in the 75k range, I went up to the beginning of my "good" data (about row 620) and copied the same formula..... and it worked!!! I'm thinking there was some sort of an Excel bug working with rows that high??? To further confuse things, I then copied the formula from row 620 down to all remaining rows in the spreadsheet, and it still worked fine - even in the very last rows that I have been fighting with all night.
The good news is that my problem now appears to be fixed. The bad news is that I am completely baffled!
Anyway, here is the now working formula, in the first column (followed by the values examined in columns J & K):
<TABLE style="WIDTH: 229pt; BORDER-COLLAPSE: collapse" cellSpacing=0 cellPadding=0 width=304 border=0><COLGROUP><COL style="WIDTH: 116pt; mso-width-source: userset; mso-width-alt: 5632" width=154><COL style="WIDTH: 55pt; mso-width-source: userset; mso-width-alt: 2669" width=73><COL style="WIDTH: 58pt; mso-width-source: userset; mso-width-alt: 2816" width=77><TBODY><TR style="HEIGHT: 51pt; mso-height-source: userset" height=68><TD class=xl67 style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 116pt; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 51pt; BACKGROUND-COLOR: #a5a5a5" width=154 height=68>Project Tracking ID (Child Project if Present, else Parent)</TD><TD class=xl66 style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext; WIDTH: 55pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: silver" width=73>Parent Project ID</TD><TD class=xl66 style="BORDER-RIGHT: windowtext 0.5pt solid; 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mso-height-source: userset" height=26><TD class=xl68 style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext; BORDER-LEFT: windowtext 0.5pt solid; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 20.1pt; BACKGROUND-COLOR: transparent" height=26>P0223277</TD><TD class=xl69 style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext; BORDER-LEFT: windowtext; WIDTH: 55pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width=73>P0223277</TD><TD class=xl69 style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext; BORDER-LEFT: windowtext; WIDTH: 58pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width=77></TD></TR><TR style="HEIGHT: 20.1pt; mso-height-source: userset" height=26><TD class=xl68 style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext; BORDER-LEFT: windowtext 0.5pt solid; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 20.1pt; BACKGROUND-COLOR: transparent" height=26>P0275078</TD><TD class=xl69 style="BORDER-RIGHT: windowtext 0.5pt solid; 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