I'm trying to programmatically write this line of code into a
macro:

=LEFT(A1,FIND("-",A1)-1)

The function shows all characters to the left of a hyphen. Anything
to the right and the hypen isn't displayed.

Ex. 12345-6789 shows as 12345

I'd like to use this function in code to highlight an entire column
like A:A and display the results in B:B.

I'd also like to ignore rows where no hyphen is found. Can anyone
help on this?

I would not use the LEFT function at all; the following will be much
quicker...

Sub GetTextBeforeHyphen()
Columns("B").Value = Columns("A").Value
Columns("B").Replace "-*", "", xlPart
End Sub

Rick Rothstein (MVP - Excel)