var course = 39;

function ruble(euro)
{
result = "";
rub=euro*course;
result = "</strong>" + rub + " руб.*/<strong>" + euro +" euro";  
return result;
}

function fromruble(euro)
{
result = "";
rub=euro*course;
result = "</strong>от " +rub + " руб.*/<strong>" + euro +" euro";  
return result;
}

function maxruble(mineuro, maxeuro)
{
result = "";
rub=mineuro*course;
result = "</strong>от " + rub + " руб.*<strong>(" + mineuro + "-" + maxeuro + " euro)";  
return result;
}