WIQL performs '+' operation inside where condition

Question

I need to retrieve work item using WIQL by REST API.
In detail I have work item type bug with the custom fields named custom.CompletedWork_1, custom.CompletedWork_2 and custom.CompletedWork_3.

Now I would like to get all the work items bug where the sum of the three fields custom.CompletedWork_1, custom.CompletedWork_2 and custom.CompletedWork_3 is different from the value of ther field Microsoft.VSTS.Scheduling.CompletedWork.

My idea is to perform a query by WIQL like this:

SELECT
        [System.Id],
        [System.WorkItemType]
FROM workitems
WHERE
        [System.TeamProject] = @project AND
        [System.WorkItemType] = 'BUG' AND
        ([custom.CompletedWork_1] + [custom.CompletedWork_2] + [custom.CompletedWork_3] <> [Microsoft.VSTS.Scheduling.CompletedWork])
		
but it doesn't work, I get the error '*Expecting comparison operator. The error is caused by «+».*'

Please can someone tell me which is the correct sintax to use into the where condition to get that the desidered workitems?

thanks in advance