Generate a form IF another cell has a specific value but otherwise use vlookup

I have posted before but i am trying to hit my problem from a different angle , heres what i am trying to do...

I enter data into a cell (Say A1) from a data validation list which includes the "Specific value"
the next cell (B1) uses VLOOKUP for its corresponding data
(C1) also does this but returns a different column

If the value in A1 is specific value (eg "*" ) from the list I would like a manual input of the values for B1 and C1

This whole process occurs around 280 times on the sheet .

I am green onthe use of VBA but recgonise it probably uses Range and ActiveCell

Can someone PLEASE help