I found a post with your reply of,

=IF(TargetTime<=ActualTime,"+ ","-
")&TEXT(MAX(TargetTime,ActualTime)-MIN(TargetTime,ActualTime),"[m]:ss")

I made it work for me like this,

=IF(C3<=D3,"+ ","- ")&TEXT(MAX(D3,C3)-MIN(D3,C3),"[m]")

The display in the cells is -0. Is there a way to format so the cell looks
blank until a calculation is made?

Also can the cell display OT if the result = 0