Textjoin help needed

[Mati44]

I tried to run this formula in excel

=TEXTJOIN(",",TRUE,IF(MID($EP3:$ET3,2,255<=6),LEFT($EP3:ET3,1),""))

but it returns error. Here in the range EP3:ET3, I have values like (L1,L2,R1,R22,R30) etc. basically alphanumeric values.
and according to the digital values I try to group letters together with textjoin which I couldn't make it work.

Can you help me with the formula what is wrong with it, or suggest me an alternative, please? Thanks.

I have excel 2010 and I use textjoin with vba code.

[p45cal]

Array-enter this (commit to the sheet using Crtl+Shift+Enter, not just Enter):
=TEXTJOIN(",",TRUE,IF(VALUE(MID($EP3:$ET3,2,255))<=6,LEFT($EP3:ET3,1),""))

[Mati44]

Thank you, P45scal. Your formula works!! I have an additional question if you don't mind.

=TEXTJOIN(",",TRUE,IF(VALUE(MID($EP3:$ET3,2,255))>=7*VALUE(MID($EP3:$ET3,2,255))<=12,LEFT($EP3:EU3,1),""))

When I tried it between the ranges with *, it didn't work. What should i do to use the formula between the ranges? instead of just <=6, between 7 and 12 for example.

[Mati44]

I tried to use and() too, but it doesn't work either.

[p45cal]

Try, array-entered:
=TEXTJOIN(",",TRUE,IF((VALUE(MID($EP3:$ET3,2,255))>=7)*(VALUE(MID($EP3:$ET3,2,255))<=12),LEFT($EP3:ET3,1),""))

[Mati44]

Thank you, P45cal. It works. Thanks for your time and help!