Forum Discussion

Possoto_Malome1's avatar
Possoto_Malome1
Copper Contributor
Oct 16, 2026

Ms project

Hello   MS project iif & switch formulas are not working please assist. I have tried a few colleagues same issue. When using IIf funtion it always returns a syntax error. Projdatediff works alright...
Microsoft Project
Kidd_Ip's avatar
Kidd_Ip
MVP
Oct 17, 2026

Microsoft Project does support IIf and Switch formulas in custom fields, but syntax errors usually occur if the formula is placed in the wrong field type or if quotation marks and separators are mismatched. The key is to ensure you are using these functions in a custom field formula (via Project > Custom Fields > Formula) and that the field type matches the return value (Text, Number, Flag, etc.).

 

https://support.microsoft.com/en-au/project/project-functions-for-custom-fields-in-project-desktop

 

Possoto_Malome1's avatar
Possoto_Malome1
Copper Contributor
Oct 21, 2026

Thank you for the response, however I am using the custom fields box using the formula below, but I keep getting errors. Please try on your side and provide an update.

IIf(ProjDateDiff(Start,[Status Date])/480>=Val(ProjDurConv([Baseline Duration],pjDays)),Val(ProjDurConv([Baseline Duration],pjDays)),IIf(DateDiff("d",[Baseline Start],[Status Date])<=0,1/100,ProjDateDiff(Start,[Status Date])/480))