Timestamp function!

I'm trying to make a function that give the time within a formula WITHOUT updating...The idea is to create a timestamp function so I can track how long it takes me to do a repetative task.

This is what I have so far, but it doesn't work :(

I'm filling in values in a column A1 and I'd like the time at which I fill in the cell to appear in the cell next to it. Later I will take the average to see how long it takes me to fill in cell in A1. I had this:

=IF(ISBLANK(A1)=FALSE,TEXT(NOW(),"hh:mm:ss AM/PM"),"")

but NOW() keeps updating, so I made the following function:

Function timestamp()
Dim tiemstamp As Date
timestamp = Text(Now(), "hh:mm:ss AM/PM")
End Function

I then write in B1, "=timestamp()", but got, "#NAME?"
had it worked, I would have changed B1 to,

"=IF(ISBLANK(A1)=FALSE,timestamp(),"")"

but my function doesn't work I guess. Any advice? Try it out, I think this would be a very useful function.

I KNOW ABOUT CRTL+SHFT+; but I dont' want to have to do this manually as I keep forgetting :p

Thank you in advance