This formula is very involved and I am not sure what to use.

Basically whether (BU25) is blank or checked determines whether or not the
rest of the formula should be used or if the field should be left blank.

Next, whether (CK24) is checked or blank determines whether the value should
be pulled from sheet ("SL 2'!E24) or ('JL 2'!E24).

Then, if (BU28) is not blank the values should be pulled from ('SL&AH
2'!E24) or if (BU28) and (CK24) are not blank then the values should be
pulled from ('JL&AH 2'!E24).

I have been trying to use =IF(ISBLANK) but I can't seem to link it all
together. What do you suggest? Should I use a different type of formula? Can
you give me an example, Please? Thanks.