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How to fix #ERROR issue in customized duration column in MS Project
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(121.6, 41%, 21%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EFO%3C/text%3E%3C/svg%3E)
Fernando Oliveira
5
Reputation points
I have a customized column just to sumarize summing the duration of a set of tasks. When I open the MPP file, the summarization lines show and #ERROR message. If I hit F9 the issue is solved. Does anybody know how to fix that?
Follow some screenshots:
a. Issue and formula used
b. Issue solved after hit F9
Microsoft 365 and Office | Install, redeem, activate | For business | Windows
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![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(243.2, 21%, 33%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EDA%3C/text%3E%3C/svg%3E)
Dan Al 0 Reputation points2025-07-29T21:03:32.3466667+00:00 I have the same issue. At least I know now that F9 fixes it. I was going in and changing the column custom fields and then changing it back to the original calculation. Hopefully you get an answer.
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