Following is the listing of VClock.def file that comes with the installation archive.
# means a comment line.
--------------------------------------------------------------------------------

# Please do not change format of the keywords even the space
# I am not that smart yet.
#
# Only change the timings and / or language name
# All figures are the timings in milliseconds that 
# indicates the appropriate sound clip in the file.
#
# All time values are the location of the sound clip
# in the VClock.WAV file. All time values must be in
# milliseconds. 
# If you do not want to give any sound clip for any
# component simply place 0 (zero) to start and end positions.
# Sound clip time formats are in milliseconds and you have to
# put them here as 'start' -> 'end' sequence .

####################################################################
####################################################################
############ Satrt of the definition ##############################
####################################################################
# Bangla or whatever you want but do not change 
# the start of the header keyword 'Bangla {'
Bangla {
    language = Bangla;

    # Ekhon Somoi Holo / It is now
    starter 34000 35278;

    # hour announcer
    hour[0]         422      1622;    # 12 & 24 hrs
    hour[1]         1691     2891;    # 1 
    hour[2]         2889     4089;    # 2
    hour[3]         4228     5128;    # 3
    hour[4]         5356     6356;    # 4
    hour[5]         6342     7342;    # 5
    hour[6]         7470     8670;    # 6
    hour[7]         8809    10009;    # 7
    hour[8]        10219    11219;    # 8
    hour[9]        11276    12276;    # 9
    hour[10]       12403    13403;    # 10
    hour[11]       26808    27658;    # 11
    
    # minutes
    min[1]    13531    14531;    # 15 min
    min[2]    14800    15800;    # 30 min
    min[3]    16068    17168;    # 45 min
    
    # Zone ( morning, noon, afternoon, etc.) If you have am pm info this shall be zero
    zone[0]    17364    18364;    # Bhor (4 am to 6 am)
    zone[1]    18633    19733;    # Sokal (7 am to 11 am)
    zone[2]    19760    20760;    # Dupur (12 noon to 3 pm)
    zone[3]    20817    21817;    # Bikal (4 pm to 5 pm)
    zone[4]    22791    23791;    # Sondha (6 pm to 7 pm)
    zone[5]    23848    24695;    # Raat (8 pm to 3 am)
    
    # AM & PM (if you have zone information it shall be zero)
    ampm[0]    0    0; # am
    ampm[1]    0    0; # pm
}

# English announcement or whatever you want but 
# do not change the header keyword 'English {'
English {
    language = English;

    # Ekhon Somoi Holo / It is now 
    starter        44414    45324; 

    # hour announcer
    hour[0]        41184    41584;     # 12 or 24 hrs
    hour[1]        35335    35835; 
    hour[2]        35851    36351; 
    hour[3]        36345    36845;
    hour[4]        36843    37343;
    hour[5]        37335    37406;
    hour[6]        37793    38443;
    hour[7]        38459    39029;
    hour[8]        39081    39496;
    hour[9]        39530    40070;
    hour[10]       40122    40572;
    hour[11]       40575    41193;
    
    # minutes
    min[1]        41572    42187;     # 15 min
    min[2]        42185    42800;     # 30 min
    min[3]        42765    43360;     # 45 min
    
    # Zone ( morning, noon, afternoon, etc.)
    zone[0]        0    0;    # Bhor (4 am to 6 am)
    zone[1]        0    0;    # Sokal (7 am to 11 am)
    zone[2]        0    0;    # Dupur (12 noon to 3 pm)
    zone[3]        0    0;    # Bikal (4 pm to 5 pm)
    zone[4]        0    0;    # Sondha (6 pm to 7 pm)
    zone[5]        0    0;    # Raat (8 pm to 3 am)
    
    # AM & PM (if you have zone information it shall be zero)
    ampm[0]        43356    43953;     # am
    ampm[1]        43913    44405;     # pm
}

End of sample

You will need to create a WAVEFORM audio file with the intended announcements. In the audio file you have to identify the relative position of the clips in terms of milliseconds from the start of the file. You may use Creative Wavestudio that comes with sound card (Sound Blaster). You can examine the original VClock.wav to findout what is the trick.