Checkbox on / off applying to cells only in the same row as the checkbox

Hi All

I am using a checkbox to merge / unmerge 2 rows of data in a worksheet (ie if the box is ticked, rows 3 and 4 unmerge to become seperate rows to enter in 2 different sets of data .... if the box is not ticked, the 2 rows are merged so that only 1 set of data is entered).

What I am struggling with is having different tick boxes relating to different rows.
the concept is as follows:
a timesheet where each day over a fortnight has 2 rows allocated to it. If the person works a standard shift, it is only 1 row that is needed, so the 2 rows for say Monday are merged into one, and they enter just one start / finish time etc.

If the person works a split shift, then they tick the check box beside the applicable day and the 2 rows "unmerge" into 2 seperate rows where a different start and finish time can be applied to each row. Therefore giving 2 start times and 2 finish times for that day.

The challenge is that i dont want all of the days to unmerge at once, only the ones that have the checkbox ticked.Timesheet check box test Darren.xlsm

Attached is a file with the 2 seperate macros (ctrl+m for merge, ctrl+n for unmerge) not yet attached to the checkbox.

Any help is greatly appreciated

Another way i thought this may be able to be done is to have the checkbox at the same level as the worksheet, so it can use a relative reference .. however i dont know how to actually do this, it is only the concept i thought may work?