password policy

I am currently generating a random password with the code below. We are implementing a password policy and I need to change the script that generates the password to match this password policy.

This is the current script:

Function generatePassword( passwordLength )
    Dim sDefaultChars
    Dim iCounter
    Dim sMyPassword
    Dim iPickedChar
    Dim iDefaultCharactersLength
    Dim iPasswordLength

    sDefaultChars="abcdefghijklmnopqrstuvxyzABCDEFGHIJKLMNOPQRSTUVXYZ0123456789"
    iPasswordLength=passwordLength
    iDefaultCharactersLength = Len(sDefaultChars) 

    Randomize 'initialize the random number generator

    For iCounter = 1 To iPasswordLength
        'Next pick a number from 1 to length of character set 
        iPickedChar = Int((iDefaultCharactersLength * Rnd) + 1) 

        'Next pick a character from the character set using the random number iPickedChar and Mid function
        sMyPassword = sMyPassword & Mid(sDefaultChars,iPickedChar,1)
    Next 

    generatePassword = sMyPassword
End Function

Password policy:

Mininum:

- 1 Upper case Alphabet
- 3 lower case alphabet
- 2 numbers
- 1 special character    ~!@#$%^+-