I have a table that looks like so:

COLA COLB
1 AB
2 CD
1 EF
1 GH
2 IJ
2 KL

I would like to use the MCONCAT(A2:A6,",") formula to look at COLA and if
equal to 1, concat those but if equal to 2 do nothing.

Like this:

AB,EF;GH