I don't have construct 2 installed at work but after reading the Deta Time expersions I'm leaning towards this soltuion:
Create a global variable for time touching (maybe TimeTouch)
On touch - > System set value Timetouch = TimeTouch + 60 * dt
On touch lease - System set value TimeTouch = 0.
I can't verify right now. Let me know if this helps.
NOTE: If you don't use dt the amount of "time" recorded will be based on frame rates. dt will allow proper time tracking regardless of frame rates. At least that's what the documentation says.