Words instead of numbers?

[Derrell Teat]

Sheet 3 has a column that only once a year has a single number value
that is copied to sheet 1 into one cell....but if no number value ha
to have the letters MNR in that cell.

Is there a formula that I can use? I've tried & its over my head!
Thanks for your time,
Derrel

 

[Peo Sjoblom]

=IF(ISNUMBER(Sheet3!A1),Sheet3!A1,"MNR")

or if you don't know where it is in column A

=IF(COUNT(Sheet3!A1:A10000),INDEX(Sheet3!A1:A10000,MATCH(TRUE,ISNUMBER(Sheet
3!A1:A10000),0)),"MNR")

entered with ctrl + shift & enter

the formulas are supposed to be in the one cell in sheet1