Try to work with numbers. And using DateDiff function.
Dates are numbers, so, it simplify your work! ;)
I will work with Jan 11th, only for rounding numbers, right?
Dim nDiasTotal as Integer, nDiasPassados as Integer
'GET DIFFERENCE BETWEEN JAN 1st AND JAN 11th
nDiasTotal = DateDiff("d", "01/01/2010", "11/01/2010")
'GET DIFFERENCE BETWEEN TODAY (ASSUMING TODAY IS JAN 6th) AND FIRST DATE
nDiasPassados = DateDiff("d", "01/01/2010", Date)
'CALCULATE PERCENTAGE OF PAST DAYS
MsgBox (nDiasPassados / nDiasTotal) * 100 & " % past time"
'CALCULATE PERCENTAGE OF REMAINING TIME
MsgBox 100 - ((nDiasPassados / nDiasTotal) * 100) & " % remaining time"