Hello Gary,

You seem to have collected your data separated by weekday already.
Aren't your 12 sheets showing Sunday data in column B, ... and
Saturday data in column H?

If that's the case you can easily apply a 3D sum:
All Tuesdays: =SUM(Sheet1:Sheet12!D1:D999)
All Thursdays: =SUM(Sheet1:Sheet12!F1:F999)

(You did not mention your sheet names. Make sure that Sheet1 is your
first, Sheet12 your last and that all the others BUT NO MORE sheets
are in between.)

If I did not guess your data structure correctly let us exactly know
how your data is organised, please.

OT: Don't ask for emails please. Others would like to participate from
all responses.

Regards,
Bernd