Feedback using analog input to control digital output

Hi all,
I've got a program that I intended to open and close two valves (and thus actuate two pneumatic cylinders) based on the readings from load cells mounted to each cylinder. The idea was that it would send a digital out to open the valve and extend a cylinder, then close the valve when the load reaches a pre-determined value (with frequency dictated by increasing or decreasing the inlet air pressure and thus the fill time of the cylinder). It would then do so for the other cylinder in a loop. The issue I have is that the response time of the loop actuating the valves was too slow-for a desired force of 1800 N I had to set the limit to 1100 Newtons. It was nice and consistent in this regard but then I started having instances where the valve would stay open long enough to apply a force of 3600+ N. The biggest need in this program is to maintain a consistent load and ensure that the max. load is not being exceeded. I've used local variables and a queue to pass the load values to the valve actuation loop but it did not seem to make a difference. I don't know if part of my problem is the mishmash of data types I'm using in passing the load cell values or if a notifier would be a better bet.
Attached is my code (LV 8.2). Thanks in advance if anyone can offer some guidance.
Attachments:
Controlled_valves.vi ‏192 KB

Here's a version in LV 8.0 and an image of the block diagram, for those running older versions of LabView.
I'd greatly appreciate any help anyone might provide as I'm getting killed here. Thanks!
Attachments:
Controlled_valves.vi ‏207 KB
Block diagram.JPG ‏177 KB

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Hi, I am Imran. I am using MCC USB1208LS. I have created the worksheet using digital input module as below and able to execute (run).
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Attachments:
present worksheet digital input only.JPG ‏67 KB
with analog input module.JPG ‏81 KB
error menu.JPG ‏77 KB

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Feedback using analog input to control digital output

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