Firstly - if an product doesn't have a min and max price set it will not reprice - so don't set min and max prices for items you know you never want to price check.
If items have a min and max set - you can turn off repricing on individual SKUs via the my inventory screen - by clicking on the title and then unticking the auto-repricing option.
You can also bulk select a number of products in the my inventory screen and use the bulk update option. For example you could filter my inventory first to only show products listed at max price or only seller etc - and then bulk update these.
If you need to update a large number of items - the best way to do this is to use the my inventory screen and filter the products first via the dropdown.
Then you can use the export option at the bottom of the screen - and export in Fixed price format - which has a field which would allow you to turn repricing off per marketplace. Then re-import this file via the bulk import screen and price checking will be turned off for all the items.
N.B. RepricerExpress will only bill you for SKUs that are actively repricing.