Calculation order - rows versus columns

Thank you for this.  Unfortunately, I still cannot get this to work...

This is the code I am using for the measure (I corrected the 'Gross Margin %' calculation as you had an additional line).

The measure is called [Var Actual CM Vs Actual-1 CM PCT] but I used the alias 'Var Adj ' in the grid.

Var Actual CM Vs Actual-1 CM PCT = 

IF(

    SELECTEDVALUE('CG: Report Income Statement'[Income Statement]) = "Gross Margin %",

    DIVIDE(

        CALCULATE([Actual CM], 'CG: Report Income Statement'[Income Statement] = "Gross Margin"),

        CALCULATE([Actual CM], 'CG: Report Income Statement'[Income Statement] = "Income"),

        0

    ) -

    DIVIDE(

        CALCULATE([Actual-1 CM], 'CG: Report Income Statement'[Income Statement] = "Gross Margin"),

        CALCULATE([Actual-1 CM], 'CG: Report Income Statement'[Income Statement] = "Income"),

        0
    ),

    [Var Actual CM Vs Actual-1 CM]
)

STEP 1:

At first the original 'Var'  column and the new 'Var Adj' column were showing the same values.  I reasoned the IF statement at the top of the 'Var Adj' code wasn't working.

IF(SELECTEDVALUE('CG: Report Income Statement'[Income Statement]) = "Gross Margin %" ...

STEP 2: 

I created a new [Selected Line] measure and added an additional column to my matrix to show the selected value:

Selected Line = SELECTEDVALUE('CG: Report Income Statement'[Income Statement])

At first, [Selected Line] did not return a value on the 'Gross Margin %' line or any similarly coded line e.g. Overheads %, Net Profit %' etc.

STEP 3:

I looked at what was unique about these lines ,and determined it was that they refer to other lines within the calculation group (as opposed to the underlying data).

DIVIDE  

(CALCULATE( SELECTEDMEASURE() , 'CG: Report Income Statement'[Income Statement] = "Gross Margin" ),
         
CALCULATE( SELECTEDMEASURE() , 'CG: Report Income Statement'[Income Statement] = "Income" ),

"-") 

STEP 4:

I experimented by modifying the 'Gross Margin %' formula within the calculation to refer to a non-existant line in the underlying data:

CALCULATE( SELECTEDMEASURE() , 'GL Map Acct Level 3'[Acct Level 3 Desc] = "XXXX")

and as expected the 'Gross Margin %' line returned the correct [Selected Line] name

STEP 5:

Having established the formula now returns the correct 'Selected Line' name I updated 'Gross Margin %'  formula within the calculation group as follows:

DIVIDE( CALCULATE( SELECTEDMEASURE() , 

KEEPFILTERS( 'GL Map Acct Level 3'[Acct Level 3 Desc] = "Income" || 
'GL Map Acct Level 3'[Acct Level 3 Desc] = "Cost of Sales" )  ), 

CALCULATE( SELECTEDMEASURE() , 'GL Map Acct Level 3'[Acct Level 3 Desc] = "Income"), 

"-")

This doesn't work 

(i) The matrix errors and refuses to display any data when the [Selected Line] measure is on the grid.

(ii) If I remove it, the 'Var Adj' measure returns a blank, not than the correct value.

By making temporary changes to the code (forcing different values in to the <alternateresult> parameter of the DIVIDE function) I have been able to determine the issue is occurring because the 'Gross Margin %' formula in the calculation group is generating a divide by zero error (although the value shouldn't be / isn't zero!) and it works in all the other columns!

I have also been able to determine that if a enter a spurious formula for 'Gross Margin %' (e.g. to simply repeat the Gross Margin value) then whilst every other column shows the wrong value (i.e. the Gross Margin value rather than percent) the 'Var Adj' measure kicks in correctly and shows the right value (0.4%).  

Conclusion: There is something about the construction of the 'Gross Margin %' formula in the calculation group that is preventing the  'Var Adj' measure from working.  It is not the DIVIDE function itself (divide by a constant works OK) so I assume it is the multiple calculate statements (which I cant avoid).

NOTE TO STEP 3:

I had previously seen a similar problem with the calculation of the 'Margin' line when the calculation was based on summing the 'Income' and 'Cost of Sales lines from the calculation group, it also summed the percentages rather than calculating them afresh on the 'Gross Margin %' line.  I got around that problem by adjusting the 'Margin' calculation to refer to the underlying data rather than other lines within the calculation group:

CALCULATE( SELECTEDMEASURE() , 
KEEPFILTERS( 'GL Map Acct Level 3'[Acct Level 3 Desc] = "Income" || 
            'GL Map Acct Level 3'[Acct Level 3 Desc] = "Cost of Sales" )  
)