Sorry, having a closer look there are a couple other issues:
-You are looking for the text, Searchstring, rather than the defined variable (remove the quotes to deal with this)
-I don't think you can use the with construct like that.
-You are telling it to look in Database.Range, I don't think Database is a valid object reference in this case
-The lookin statement is for whether to look at the formulas or results I think, if you want to limit to a column, you need to change the range the find method is applied to.

Maybe try:
Sheets("Database").Range("B1:B100").Find(What:=SearchString, LookIn:=xlFormulas, LookAt _
        :=xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, MatchCase:= _
        False, SearchFormat:=False).Select