I am having problems with some JavaScript in a form I am putting together. I require the script to set the value of the text field 'mla6' in the form 'cq' to the combined total of the values in 'mla2' and 'mla4'.

Well, "+" is used for combining string values too. You should get the integer value of the fields;

there is a function written as "parseInt(value)" in javascript but it doesn't work in old mac browsers, so it's better to use javascript flexibility in data types.

Simply multiply a value with "1" to get it's integer value, It will be as follows in your code

document.cq.mla6.value=(document.cq.mla2.value*1)+(document.cq.mla4.value*1);

try it and see the result.