Capture Elapsed Time from User, and Multiple occurrences of same task

I admit I am quite new to the BPMN model. We have incorporated the engine for some workflow integration, but I cannot how to model the following scenario.

Lets says I have a task user task “Configure Router”, followed by another user task “Confirm Access”, after which there is a gateway such that if the user cannot access something it cycles back to the “Configure Router” task.

For the Configure Router Task and Confirm Access task, I want to capture a value from the user to reflect the time they spent. This time may have include time not in workflow, and interrupted, so not trying to build any “start/stop” function at this point, but simply let the user enter a value, like “12:30” for 12 hours, 30 minutes. We can use a custom data type on the form variable to collect the time value, although when going back to collect the history to rebuild the sequence for the process later this gets more complicated.

But the real challenge is, if the user “fails” access and enters 0:30 (30 minutes), it will re-enter the “Configure Router” task, where a tech now sees their original time spent (variable name the same) of “12:30”, but now they spent another 6 hours (it’s a really slow tech). Either they MANUALLY sum up time spent and change the variable, or I cannot tell the total time the tech has spent. If they put in 6 it will over-write the 12:30 and I will not see it at the end.

Trying to understand the best way to capture multiple instances of the same value when loops occur in a workflow, as well as if there is any existing solution for “elapsed time” value that someone has worked out.