An estimate of the amount of effort required for a project can differ greatly from the calendar time needed to complete the project. While you can accurately estimate that a VI takes only two weeks to develop, you still need to fit that development into the overall schedule. Remember that you will have meetings and other events during the development time. If you have other projects to complete first, or if you need to wait for another developer to complete his work before starting the project, then you must factor extra time into the schedule.
Estimate project development time separately from scheduling it into your work calendar. Consider estimating tasks in ideal work days, which correspond to eight hours of development without interruption.
After estimating project time, try to develop a schedule that accounts for overhead estimates and project dependencies. Remember your other responsibilities and tasks, such as weekly meetings to attend, existing projects to support, and reports to write.
Record progress meeting time estimates and schedule estimates. Track project time and time spent on other tasks each week. This information probably varies from week to week, but determining an average is a useful reference for future scheduling. Recording this information helps you plan future projects accurately.