Cols A thru M have varying widths.

Cells A1 thru M1 contain data.
Cells A2 thru M2 are empty.
Cells A3 thru M3 contain data.

I want each cell in A2 thru M2 to contain a string of dashes (i.e., "-"). Each string must have the same length as the column-widths in the adjacent columns.

How do I do that?