add an "or" statement

Right now I have the following script in my form:

//</ACRO_script>
//</AcroForm>

//<AcroForm>
//<ACRO_source>AreaDuesQty:Calculate</ACRO_source>
//<ACRO_script>
/*********** belongs to: AcroForm:AreaDuesQty:Calculate ***********/
var A = +this.getField("ChptTotQty").value;
var B = +this.getField("AffTotQty").value;

if( A > 0 ) event.value = A + B;
else event.value = "";

It works great as long as there is a number in the "ChptTotQty" But, I want it to give me a number whether there is a number in "ChptTotQty" or "AffTotQty" field. Is there a way to make "if ( A > 0 ) event.value = A + B;"  Into "if ( A > 0 ) or ( B > 0 ) event.value = A + B;"

Any help would be greatly appreciated.

Thank You