Hello,
Actually i don't have a Vbscript for your requirement but i have javascript.
Please check it and convert it in VBscript if you can.
but this script surely give you desired output.
var txt = "GUJ 12.50 VAT";
var numb = txt.match(/\d+./g);
numb = numb.join("");
alert(numb);
//You’ll get 12.50 in numb….
Please let me know it is useful for you or not?