Formula for time sheet kinda??

I am having an issue with a formula. I have column A, where it is a user inputed time (ex:0000-2359) for what time a person clocked in. In column B it is how much time they have accumlated this week also user inputed(ex:35.30). In column C I need have a formula that tells me when they need to clock out(ex:0000-2359).Any help would be greatly appreicated.

meh..... I will just go back to nxportal where my title above is okay and people know what I mean. Should have checked there first anyway. Please delete my account.The title rule is retarded, I am pretty sure you know what I mean by my title, that is why peole explain in the body of the message. Just another example of people letting their mod power going to their head.