MDX - Sum one measure at leaf lvl where another measure exists at leaf lvl - mdx

Question

I need to work out Stockturn at any lvl in an item hierarchy.
So far the calc is SUM the last 3 months [COGS] * 4 divided by [SOH] (SOH Value)
The below is embedded in a BI tool and works. It is in the Item grid and filters for every member in the Item dimension at the level display:
((SUM({.lag(3):.lag(1)}, ([Type].[Type].[Actual], [Measures].[Cogs]))) * 4) /
([Type].[Type].[Actual], [Measures].[SOH], )
What it needs changed/added is only returning [SOH] for Items where the [COGS] measure has values.
So if I have items that do not have COGS then do not include them:
Item
SOH
COGS
A
10
20
B
15
40
C
20
Do not include C as it will throw the calc.

Answer 1

The simplest approach - assuming you are using SSAS 2012 or newer - would be to use Divide instead of the division operator /:
Divide( ((SUM({.lag(3):.lag(1)}, ([Type].[Type].[Actual], [Measures].[Cogs]))) * 4),
([Type].[Type].[Actual], [Measures].[SOH], )
)
Divide returns NULL (empty value) instead of infinity when dividing by zero or null.
Edit: I see you want to avoid the calculation of the numerator is null or 0, not the denominator. In this case, you would use Iif:
IIF((SUM({.lag(3):.lag(1)}, ([Type].[Type].[Actual], [Measures].[Cogs])) <> 0,
((SUM({.lag(3):.lag(1)}, ([Type].[Type].[Actual], [Measures].[Cogs]))) * 4)
/
([Type].[Type].[Actual], [Measures].[SOH], )
, NULL)
Iif is a function with three arguments, a condition, the value to use if the condition is true, and the condition to use if the condition is false.