Rounding Time into 30 min increments

Hi All,

I have attached a spreadsheet with an example.

I am looking into time worked to charge as labour. we charge by 30 mins blocks, although the 1st 30 mins are within the Call Out then the extra 30 mins are chargeable.

I need help in once you've entered a new 30 min block it rounds up for charging purposes. then I need to work out how many 30 mins blocks, after the first have been 'used'. then turn this into a normal number to use in the charging calculation.

i hope this makes sense

i look forward to your help.

i have a feeling this is simple, but I've tried alsorts to no avail.

Cheers

Donna