I realize you cannot do a simple IF statement like in regular Excel.
Goal:
A field in a dimension has a 'Y' or 'N'.
If it says 'Y' then: 100
If it says 'N' then: CALCULATE(DIVIDE([Job Line Costs To Date],SUM('JOB COST DETAILS'[Job Line Estimate Cost Amount])),Job[Job Comp Y or N]="N")
Goal:
A field in a dimension has a 'Y' or 'N'.
If it says 'Y' then: 100
If it says 'N' then: CALCULATE(DIVIDE([Job Line Costs To Date],SUM('JOB COST DETAILS'[Job Line Estimate Cost Amount])),Job[Job Comp Y or N]="N")