How to calculate build time

[maorlast2]

I created these build time events

Application.Macros(vbldTemporary).Add "START_TIME", vbld_FormatTime()
Application.Macros(vbldTemporary).Add "START_TIME_EX", vbld_FormatDateEx(now,"hh:MM:SS")

Application.Macros(vbldTemporary).Add "END_TIME", vbld_FormatTime()
Application.Macros(vbldTemporary).Add "END_TIME_EX", vbld_FormatDateEx(now,"hh:MM:SS")

(_EX means that this is expression that i print in the log)
How can i calculate the build time?