Making Project field Mandatory based on Line Category

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Hi All,

We have one requirement where customer wants to have Project task field as Mandatory based on Requisition Line Category.

Means if in a Requisition we have Line category as X or Y, the Project field should be Mandatory, and if we have category as A or B, the Project field should not be Mandatory.

We have a note which says that customization is not possible. 

PRC:SSP: How to Update Certain Fields on a Page Based on a Value Selected from Another Field? (Doc ID 2745392.1)

But still open for suggestions.

Thanks and Regards,

Vikash Sharma