IsNumeric command

No worries, the virtual table below creates the data set and so no data tables are needed to run this query. . . .

Select
TestVariable = case when isnumeric(org.OrderAmountRangeQty)= 0 then org.OrderAmountRangeQty
else 'Its a number' end
from
(
Select OrderAmountRangeQty = 'Z'
union all
Select OrderAmountRangeQty = '1'
union all
Select OrderAmountRangeQty = '15'
union all
Select OrderAmountRangeQty = '#2'
union all
Select OrderAmountRangeQty = '3'
) as org
-- isnumeric(column) = 0 means it's not a number
-- isnumeric(column) = 1 means the column value IS a number

Similar functions: IsDate identifies if the freetext field is a date.