Is it possible to do Glacier express from BO region?

Not really. The Glacier Express is best done in order to get East-West in Switzerland, Doubling back would make it a very long day.
Look at the map here: https://www.sbb.ch/content/dam/sbb/de/pdf/geschaeftsreisen/reisen/Uebersichtskarte_Synoptic_Map_2018_einseitig.pdf

Wengen is slightly left and below centre, just below Interlaken. A straight line due south from Wengen would get you to the starting point (Brig), but you would need a helicopter, there are some rather big mountains in the way. ☺
The route would be (times from SBB website: https://www.sbb.ch/en/ )

• Wengen - Interlaken - Spiez - Visp - Brig (2h07, e.g. depart Wengen 08:03, arrive Brig 10:11)
• You are now on the Glacier Express route (Skipping the first bit from Zermatt): Brig - Andermatt - Chur (4h04 Brig 10:18, Chur 14:15)
• Now back to Wengen by the longer but faster route around the Alps Chur - Zürich - Bern - Interlaken - Wengen (4h10, Chur 14:39, Wengen 18:49)

A very long day!

If the purpose of the day is just to ride trains, the answer is yes. Early start will get you to Brig, in time for the 10:18 GEX toward Disentis/Muster. Return from there, that is the best part of the GEX, on regular trains, to avoid paying the reservation fees both ways. If you have time (and daylight and good weather), take the Loetschberger train from Brig to Spiez on the way back. Little bit longer, but much more scenic.

In your other thread, you were also considering the Golden Pass scenic route. I thought it might be faster, but it's really not. In that example, traveling Wengen-Interlaken-Speiz-Zweisimmen-Montreux takes 4.5 hours and returning via another route can be 3.5 hours.

Thanks a lot Chris and Sam for your valuable suggestions. I'll check the details given by you both.
Hi Laura. Thanks for your reply. Yeah i wish i could do either golden pass or glacier express. Since i stay five days in wengen and if the weather is not good for mountain peaks, i thought i can plan any of these scenic rail journeys in a day.But both seems to be long and tedious from Wengen.

Yeah i wish i could do either golden pass or glacier express. Since i
stay five days in wengen and if the weather is not good for mountain
peaks, i thought i can plan any of these scenic rail journeys in a
day.But both seems to be long and tedious from Wengen.

Siva, if you're mainly looking for something to do if you don't have clear weather for mountain views from Wengen, here are my "rainy day" recommendations near Wengen:

Trummelbach Falls:
http://www.truemmelbachfaelle.ch/e/index.html
It's a spectacular series of waterfalls INSIDE a mountain. (I've only seen it in the summer, so I don't actually know how big the falls are in April.)

Ballenberg "living" museum:
https://www.ballenberg.ch/en/

Boat ride on Lake Brienz from (village of) Brienz to Giessbach Falls, and the funicular up to the hotel and path to the waterfalls:
https://www.myswitzerland.com/en-us/the-giessbach-falls-brienz.html

Boat ride on Lake Thun

Thun Castle and Thun's Old Town:
https://www.myswitzerland.com/en-us/thun-castle.html

Aareschlucht gorge (During April use the west entrance/the Meiringen end):
https://www.aareschlucht.ch/en/Welcome#.WjmYCSPMxsN

I've not been to Switzerland in April, but they all appear to be open then, from their web sites.

Hi LindaL,

Thanks a lot for your wonderful links. Very informative. Exactly what i was looking for, activities around jungfrau region if weather is not good for peaks.

Thanks again!!
Siva