You are probably looking for a number of parameters.
You could then create a calculated field to "summon" the desired parameter in the appropriate case.
You'll want a different parameter for each value that can be independently set.
In the example, you attached, you appear to have 8 "boxes" that could hold inputs.
I think you could create a calculated field as "Growth Over 3 Years w/ param":
[Total # of Staff] *
IF [Occupational Groups] = 'ABC' THEN [Annual Growth ABC]
ELSEIF [Occupational Groups] = 'DEF' THEN [Annual Growth DEF]
ELSEIF [Occupational Groups] = 'GHI' THEN [Annual Growth GHI]
ELSEIF [Occupational Groups] = 'MGMT' THEN [Annual Growth MGMT]
and then you could create another calculated field as "Term Over 3 Years w param" similarly.
Hopefully that helps get your going. If you need more help, please attach a packaged workbook with your example.