You can use the Ports and Pins in Mach if you want or you can use the modbus in the CSMIO or you can use some of each. What you can not do is use the same i/o for both, it is one or the other for that particular input or output.
What I mean is, for example.
If you had an input to the CSMIO you could set it in Ports and Pins in Mach and use it in VB but you would use the standard Mach VB way of doing things.
So say you have the Input set to Input 1 in ports and pins you would then be able to use the VB with something like
If IsActive(Input1) then..........
If you use it via the CSMIO Modbus then you do not set the Input in Ports and Pins, you simply use the modbus in the CSMIO, so it would be something like
If GetInBit (*,*) then........
Hope that helps

Hood