for loop with if statement

Morning all.
I'm looking to set up an automatic password sheet protection tool and there
are only specific elements that I need protected on the worksheets in my
workbooks.
As such, my goal is to look for a value, in a single column, and if the
value exists in one cell, protect that row. All other rows will remain
unprotected.

As I think about this, it seems to me that I'd need a for loop to iterate
through the rows of that one column, and then use an IF statement to look for
a value.

Part of my struggle is that not all worksheets start at the same start row.
Nor do all worksheets end at the same row. Therefore, I need a variable to
delineate my start and end points. I've already learned that LastUsedRow does
not work well enough to use for this.

E.g.
for i = firstusedrow to lastusedrow step 1
if .cell() "" OR " " then
Activesheet.protect.........

Your helps are appreciated.

My mistake-- I didn't realize this posted to worksheet function until AFTER I
hit the post key. Ignore this post.