How do I populate date cell based on the sum of two time cells.

Hi all,
Firstly, thanks to all for your valuable time taken to check out my issue, and help me with my dilemma.
My apologies if this is listed as another post somewhere, I did do a search and have a look, but couldn't find anything specific to what I need.
To hopefully assist, I've attached an example workbook.

Trip Plan example.xlsx

I'm trying to work out how to have cells R11 - Rxx generate the correct date, based on the rest of the calculations.
Please note that the attached is a crude cut down version of the larger spreadsheet, for the purpose of highlighting my problem.

SO, if E7 is changed, subsequently the values in K11:Rxx will be respectively updated.

D12 and G12 are entered manually. (although I'll probably make these drop downs or date choosers at some point...)

Depending on the value in E7 and time in D12, the required break period is listed in K11: Kxx.
The time that these periods of rest are required to occur before is then calculated and listed in O11:Oxx.
I need R11:Rxx to calculated the appropriate date from these calculations, relative to the date in G12.

For example, the rest required in K11, is required on the same day, as such it need to populate with the value in G12.
However the rest required in K13:Kxx, is required by a time (O13:Oxx) on the following day - G12+1
In some case, this time variance could run over 2 or more days.

I figure it's got something to do with the value in D12 also including the date of 0/1/1900.

I'm happy to add hidden cells for formulas/results to work around it, as the end product will print as an A4 document, where many cells will be locked.
Would prefer not go with any VBA unless it's my only option as I haven't done any VBA stuff as yet.

Thanks again for your time, Hopefully this all make sense.


NB (the value in P5 is static only in this example)

Thanks for your input Glenn,
Ideally I'd like to use drop down lists/Chooser for the entering of the date and time. Is this possible with the method that you have offered.
I have tried the Microsoft Date and Time picker but don't really know how to (or if you can) choose a date and a time simultaneously from it.

The suggestion you've offered works well so long as the date/time is in the same field.

I'd like to use a drop down list for the time value in D12, and a date chooser for the date in G12.
Or, is there a date/time picker available that will allow me to select both the date and time for D12 as per your suggestion?

The workbook (when completed) will be used by a number of people with various computer skills. I need to keep the entry of data as simple as possible.
I can see manual entry creating headaches for me....

OMG..... It was sooooo simple!!!!! Hahaha

Thanks a heap Glenn!!

Ummm OK... so next question is how do I close this thread as Solved and give you credit?