Calculate the compilation time

[teognost]

I have a step for a C# solution compilation.I would like to write in log the time in seconds passed during the step execution.It is easy to write "Step started at ...,ended at ..." -but how can I write now many seconds passed between start and end?
I look at some VBScript Date\Time fctions here :
http://www.w3schools.com/vbscript/vb..._functions.asp
but I didn't see anything interesting.