i have a cell which currently has "=sheet1!A4" & "units". I would like to
know how i can format this to where the number value in the cell contains
a
comma seperator. like if the value of A4 is 34,000, the result is "34,000
units" instead of "34000 units".

Give this a try instead...

=TEXT(Sheet1!A4,"#,##0")&" units"

Rick