Microsoft office form add Time duration field

EdisonDevadoss I am also looking for a duration but on the Excel workbook after the FORMS are answered.

I've found that it faults in two primary ways. 

One by formula pattern change within the form column value area.

I use the FORMS input to the data in cells of the C column with a start time, and a manual text or drop down entry in another column that causes a time stamp. That formula is: =IF(P2<>"",IF(Q2<>"",Q2,NOW()),"")   Both C2 and Q2 have the same time and date formatting: m/d/y  hr/mm
To get the difference I use the next formula
=TEXT(Q1-B1,"d:h:mm") is in R column and it works out fine for the initial cell.  But upon using the FORM and submitting, the excel adds another line and changes the formula values to =Q1-B1  and the presented time difference is then off.  Without using FORMS the logic and pattern =TEXT(Q1-B1,"d:h:mm") holds and the display time Days-Hours-Minutes comes out correct. Then when using FORMS to fill out further queries it interjects a new Time formula: =Q1-B1 for all of the following rows
That new formula shows an incorrect format and the duration is then off for each row. Basically FORMS changes the forumula from =TEXT(Q1-B1,"d:h:mm") to =Q1-B1
It skews what we are after.

Next, I tried to work outside of the Form row and question set column input areas.  Off to the right and enter  =TEXT(Q1-B1,"d:h:mm") to the right of the last FORM input data column.  I even gave it 4 or 5 empty columns as a buffer.  It is apparent that excel uses a spacer row on the bottom of the last entered form record.  Any independent column of autofilled patterned formula will be broken and offset by that FORMS input row formatting.  That destroys the automation of the need to category times and durations.  

Is there any way around this or an outright fix for it?