Question:

I've created a new form within which users can view product details. In most cases there is an accompanying image for the product stored on our web site.

As such, I've created a button that when clicked opens a web browser and displays the image.

 I would like to disable the button if the image does not exist, is there any way of checking the URL when the form opens, and disabling the button if the image is not there? 

Answer:

1) Copy this function and either place it in your form script or in a library that it references (preferable, as you can use it again elsewhere)

Function Web_ValidateURL(strURL)

Dim objHTTP
Set objHTTP = CreateObject("Microsoft.XmlHttp")
objHTTP.open "HEAD", strURL, FALSE
objHTTP.send ""

if objHTTP.Status = "200" then
Web_ValidateURL = True
else
Web_ValidateURL = False
end if

set objHTTP = nothing

End Function

2) In the script for your form, or wherever you want to check a URL...

if Web_ValidateURL("http://www.yourwebaddress/yourjpgfolder/xyz.jpg") = True then
btnImages.Enabled = True
btnImages.Caption = "Images"
else
btnImages.Enabled = False
btnImages.Caption = "No Image"
end if

... you will obviously need to change the code to suit your circumstances but hopefully the above is simple enough to understand.