VBScript read a float from a file stream

Is there any pure VBS /wsh way to get 4 bytes from a string that form an IEEE floating point number and return them into a single typed variant? I have done it by building the IEEE number from its bytes but its painfully slow...

function bintofloat (str,i)  'string, position
    dim n1,n2,exponent,mantissa,sign
    'only normalized, does'nt detect infinity or NaN
    const m_sign= &h8000, m_exp= &h7f80
    const d_exp= &h800000& , m_mant=&h7fffff&
    n1=asc(mid(str,i+3,1))* 256 + asc(mid(str,i+2,1))
         exponent = ((n1 and m_exp)/&h80)
    sign=1+ 2*((n1 and m_sign)<>0)
    n2 = ( asc(mid(str,i+2,1))* 256 + asc(mid(str,i+1,1)))* 256 + asc(mid(str,i,1))
    mantissa= (n2 and m_mant)
  wscript.echo mantissa,exponent
  if exponent=&hFF then   'nan o inf
     if mantissa=0 then 
        'bintofloat=sign * 1e38
        if sign then bintofloat="-Inf" else  bintofloat="Inf"
     else        
        bintofloat ="NAN "& mantissa
        'bintofloat=sign *1e38
     end if   
   elseif exponent =0 then 
    if mantissa=0 then
        bintofloat=0 
    Else  'denormalizad
      bintofloat=sign* mantissa * 2.^-149
    end if      
   else
     bintofloat =  sign* (mantissa or d_exp) * 2.^(exponent -150)
   end if   
end function