Including timings on score and parts

[vyvyanhs]

Hello,

I'm writing a cut-up style score (different players playing loops ad lib in different time sigs, lots of senza tempo etc) and want to include approximate timings for guidance, eg "1min 30 " at the top of a system with a dotted vertical line running to the bottom. This needs to show up in score and parts. There is a video> timecode option but this is far too precise and displays figures for every bar, I probably need a figure every 30 seconds or so. The vertical line needs to "pass behind" staves with notes on to avoid visual confusion. Ideally the line would stay at the correct place, ie the "1 min 30" marker would stay at 1 min 30 sec through the score even if I change tempo or add bars.

Any ideas how to do this? Thanks in advance,

Vyv