How to set bar #1 at specific timecode?

I’ve got this project which was timecode based with a lot of clips, fades and edits in it. AND: I’ve locked all clips’ positions.
Its starting timecode = 01:00:00:00 and its original tempo was 120BPM.

Now this composer gave me stereo mixes of his work which I want to implement in my project, but I want to create tempo maps (which differ from the original tempo) and signature-changes according to the music. This is because I want to have my delays synced to the projects’ tempo.
I still want to have my project start at timecode 01:00:00:00 of course, and I want to keep my first bar at timecode 01:00:00:00, but as soon as I start to create tempo-changes, Nuendo moves the bars of course. How can I now instruct Nuendo to move bar #1 back to 01:00:00:00 ?

When I use command Edit/ Project Setup/ Display Bar Offset, I can’t position the start position of bar #1 precisely enough because “Display Bar Offset” only works with whole bar numbers…I wish there was just a simple command like “Set bar number at cursor”.

When I work the other way around and use “Set Timecode At Cursor”, my locked clips won’t move to their new position, so this command is useless in my project.

Any suggestions?
thanks, Niek/ Amsterdam.