It sounds like you do need a conditional bool that you can unlatch after either the PV or the SCADA has sent a new SP. I have to do something similar with a SCADA permissive in some cases where if a shutdown occurs, operators cannot just start it back up. Unfortunately Cygnet SCADA requires a good bit of scripting to make a momentary pushbutton, its easier to unlatch from the controller.
For Example, Have both the SCADA and the PVP write the setpoint to the tag SP_HMI (int, or real, or whatever)
rung 1) if SP_HMI > 1, SP_BOOL (OTL)
rung 2) if SP_BOOL then MOV SP_HMI to the desired Setpoint tag
Rung 3) if SP_HMI > 1 and SP_BOOL then OTU SP_BOOL and branch around the OTU to add a second “output” of MOV 0 to SP_HMI