Zip code error, Need help if zip starts with zero

I have been using a "get distance" VBA to calculate the distance between two zip codes (can work with city names as well) that links to a google api.

I stumbled upon a calculation error yesterday that occurs when a zip code begins with a zero. The VBA is ignoring that 0 and just picks up the rest of the numbers. I think what I need to add is something like

If length of start does not = 5, then start needs to have however many zeros added in front of the number until length = 5

(attached file, see row 4, - link should be creatinghttps://maps.googleapis.com/maps/api...j8SzHMSMltzQC4, but instead is creating https://maps.googleapis.com/maps/api...j8SzHMSMltzQC4)

VBA is

Public Function GetDistance(start As String, dest As String)
    Dim firstVal As String, secondVal As String, lastVal As String
    firstVal = "https://maps.googleapis.com/maps/api/distancematrix/json?origins="
    secondVal = "&destinations="
    lastVal = "&mode=car&language=pl&sensor=false&key=" & Range("KEY")
    Set objHTTP = CreateObject("MSXML2.ServerXMLHTTP")
    Url = firstVal & Replace(start, " ", "+") & secondVal & Replace(dest, " ", "+") & lastVal
    objHTTP.Open "GET", Url, False
    objHTTP.setRequestHeader "User-Agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)"
    objHTTP.send ("")
    If InStr(objHTTP.responseText, """distance"" : {") = 0 Then GoTo ErrorHandl
    Set regex = CreateObject("VBScript.RegExp"): regex.Pattern = """value"".*?([0-9]+)": regex.Global = False
    Set matches = regex.Execute(objHTTP.responseText)
    tmpVal = Replace(matches(0).SubMatches(0), ".", Application.International(xlListSeparator))
    GetDistance = CDbl(tmpVal)
    Exit Function
ErrorHandl:
    GetDistance = -1
End Function

So, what I am trying to figure out in the VBA is how to make it so that if "start" and/or "dest" begin with a zero, how to make it look at start and/or dest as "0"+start

Help!

I punched in the zips for Boston (00215) and Pasadena (91106 where I am) and got 3229 miles

You can simply use Format()
ex:
start = Format(start, "00000")