The below scrips mandates the fields in worklog.
1. Open a notepad
2. Paste the below scrips and save as CustomScripts.js under <SDP-home>/custom/scripts folder (If you already have any scrips under existing CustomScripts.js, please take a backup)
3. Please clear the browser cache once and then try to add a worklog
************ Mandate Time Taken to Resolve Field **************
jQuery(document).on('click',"#addWorkLogButton",function(){
var fields = ["timespenthrs", "timespentmins"];
var isMandate = true;
for(var i=0;i<fields.length;i++){
var fld_val;
if(fields[i]=="timespenthrs" || fields[i]=="timespentmins")
{
fld_val = jQuery("[name='"+fields[i]+"']").val();
}
if(fld_val != "" && fld_val != "null" && fld_val.trim()!=""){
isMandate = false;
}
}
if(isMandate){
alert("Please enter the Time Taken to Resolve");
return false;
}
return true;
});
************** Mandate Description **************
jQuery(document).on('click',"#addWorkLogButton",function(){
var fields = ["description"];
var isMandate = false;
for(var i=0;i<fields.length;i++){
var fld_val;
if(fields[i]=="description")
{
fld_val = jQuery("textarea[name='"+fields[i]+"']").val();
}
else{
fld_val = jQuery("[name='"+fields[i]+"']").val();
}
if(fld_val == "" || fld_val == "null"){
isMandate = true;
}
}
if(isMandate){
alert("fill worklog and description");
return false;
}
return true;
});

There is already a feature developed by SDP that may serve the customer's requirement. Please check SDP Issue ID: 70934 for more information.
This feature has been released in SDP - 10001 and it will be available for us when we release MSP 10.5