Making a program to find the square root of any number

Does anybody know how to code a program to find the square root of any number I put into a textbox.
I have text1 as the input box
text2 as the answer box
and command1 as the button to find the square root

I also need to know if anybody can make a program to solve for a variable using the same items for like input and that and i want it to solve stuff like
X*5=2x+20-2x
stuff like that

i would like the coding for both but either one is fine if anybody knows how

Here's the first part.

Code:

---

Function CalculateSquareRoot(NumberArg As Double) As Double
  If NumberArg < 0 Then  ' Evaluate argument.
      Exit Function  ' Exit to calling procedure. 
  Else
      CalculateSquareRoot = Sqr(NumberArg)  ' Return square root. 
  End If
End Function

---

First question: use either one of the two lines:
MARTY WAS SECONDS FASTER :(

X^0.5 works fine too.

Third root:

X^(1/3)

For the second part, i'm just working on a ActiveX Dll that does that.