Formula to display blank if 2 cells are blank

I have a formula in Cell (F11) that looks to see if (A8) is blank & if so - returns a blank, But I would like it to also if the other Cell happens to be blank to also return the destination cell blank.

If (A8) blank & (F4) Not return blank - no calculation

If (A8) Not Blank & (F4) blank - no calculation

Both Cells Have there proper #'s return Calculation

right now I have it to where it just checks to see if (A8) is blank




=IF(OR('Job Ticket'!A8=""),"",F4-'Job Ticket'!A8+1)