Time issue

i hope someone out there can help me or point me in the right diection. i am quite new to Excel so please forgive me for sounding dumb (still learning) i need to know how to complete a time arrival sheet. example-

A B C D
Vehilcle. due at. arrived at. minutes late.
A Lorry 18:00 18:25 25
A Car 19:00 19:15 ??

I would like to acheive that column D shows minutes late/early after inputting arrival time, Also, can colum C show the time of arrival at the present time and not be changed once the arrival time has been entered. i hope someone out there can help me this will make things at work so simple. Many thanks

segger

can colum C show the time of arrival at the present time and not be changed once the arrival time has been entered

can the arrival time be logged as actual time of arrival. where by this cannot be logged as any other time. for instance say--A Lorry due at 18:00 but arrives at 18:30. the person recording the time of arrival cannot log this arrival as 18:00.
hope you canhelp


many thanks