Count the number of cells in a column containing a dash for Google sheets

[mariehz]

I want to check my data knowing that they are okey when they contain a dash. My data is in another spreadsheet so I use the "importrange" formula.

I tried the following formula: =IF(LEN(IMPORTRANGE($B6,"LICENCES!C2:C"))-LEN(SUBSTITUTE(IMPORTRANGE($B6,"LICENCES!C2:C"),"-",""))=1,"OK","NOT OK")
But it only took into account the first cell of my column and not my whole column...

I also tried another formula in which I made the difference between the number of cells containing a value in my column and the number of cells containing a dash in my column knowing that if the difference is equal to 0 then my data is good. But my formula didn't work because the dash part was wrong.

I don't know if my problem is clear.

Thanks to those who can help me answer my question