Fast Square Root Calculation?

[Alphanos]

Can anyone make this faster?

Public Function SquareRoot(ByVal Number As Double) As Double
 
If Number < 0 Then Number = Number * -1
 
Dim i As Long
Dim Temp As Double
Dim Power As Long
Dim Estimate As Double
 
Temp = 1
'Calculate an initial Estimate
If Number >= 1 Then 
    Do While Number > Temp
        Temp = Temp * 10
        Power = Power + 1
    Loop
Else
    Do While Number < Temp
        Temp = Temp / 10
        Power = Power - 1
    Loop
End If
 
Power = Power / -2
Estimate = 10 ^ Power * Number
 
'Calculate actual square root
Dim OldEstimate As Double
 
Do
    OldEstimate = Estimate
    Estimate = 0.5 * (Estimate + Number/Estimate)
Loop Until OldEstimate = Estimate
 
SquareRoot = Estimate
End Function

(Wrote this just now, so I haven't debugged it; I'll go check it now but I want to post it first just in case I get a BSOD.)