function vat_calculator(c){var af=strip_common_elements(document.getElementById(c).calc_amount.value);var aM=document.getElementById(c).vat_already_added.value;var bd=0;var bt=0;var aI=0;if(!check_number_valid(af)){alert("You must fill out the amount you wish to calculate VAT on before you click submit");return false;}if(aM=="yes"){aI=af;bd=((af/117.5)*100);bt=(aI-bd);}else if(aM=="no"){bd=af;bt=((af/100)*17.5);aI=(af*=1.175);}document.getElementById(c).output_net.value=format_number_output(bd,2,',','£');document.getElementById(c).output_vat.value=format_number_output(bt,2,',','£');document.getElementById(c).output_gross.value=format_number_output(aI,2,',','£');return false;}