I want to be able to use a range reference of cells as text in one cell by a
function in another cell. I can create the range using CONCATENATE (e.g.,
A310:A320) which will appear as text in a cell, but I can't seem to use this
in another function call. Does anyone know how to use this range of cells
listed as text in one cell in a separate function call?

I've tried using CONCATENATE within the function and also with & symbols but
the function won't work.

The following doesn't work and replacing the range specifications with
CONCATENATE equivalents doesn't seem to work.

= FORECAST(50,"A"&B18&":A"&B19,"B"&B18&":B"&B19)

B18 and B19 have the proper numbers for the row and columns.