How do amend a basic sum function not add a sub-table field based on another field?

I currently have a basic sum formula that totals all of the 'Item Total Net' fields within a sub-table as shown on the attached screen shots, however i would like a formula that omits any of the figures that have been ticked as a provisonal cost in a seperate field.
i have tried the follwing code but it keeps on indicating that there is a symbol missing after 'where', any suggetions?
sum(select 'Section 1 Items'.'Item Total (net)' where 'Section 1 Items'.'Provisional Cost' = 0)

Try:
sum(select 'Section 1 Items'.'Item Total (net)' where 'Provisional Cost' = "False")
Or (without the ")
sum(select 'Section 1 Items'.'Item Total (net)' where 'Provisional Cost' = False)
Steven.

Great, i'll try that.

Yeah it keeps on saying symbol expected at... which was what it was doing earlier? any ideas?

which is directly after 'where'?

Maybe this is Better:
---
let i := (select 'Section 1 Items' where 'Provisional Cost' = False);
sum(i.'Item Total (net)')
---
ps: can you try if this works also:
---
sum((select 'Section 1 Items' where 'Provisional Cost' = False).'Item Total (net)')
---
Steven

Nearly, but it adds the same amounts up for all the different quotes making all the sums for section one the accross all of them?

*Makes the amounts in section one the same accross all the quote numbers.

This might do it:
---
let me := this
let i := (select 'Section 1 Items' where 'Provisional Cost' = False and Id = me);
sum(i.'Item Total (net)')
---
Steven

Problem solved, i ended up not too sure by luck (more of a process of elimination) adapting the follwing:
sum(select 'Section 1 Items'['Provisional Cost' = 0].'Item Cost Total') this as per previous formula's ending up selecting all the records within the table, literally adding up all the section 1 costs across all invoices, i just removed the 'select' statement and now it seems to be working seemlessly.
sum('Section 1 Items'['Provisional Cost' = 0].'Item Cost Total')
Thanks for all your help Steven.