I am programming VBA. An interface I need to use here accepts arguments only if they are type "object". To use it I need to fill a string like "abc" into that variable. This always brings something like typemismatch.
dim varName as Object
Set varName = "My Text"
same problem when running
dim varName as Object
varName = "My Text"
I haven't found any conversion and have no idea how to solve
It sounds like you're referencing a .NET library, in which case System.String inherits from the generic System.Object. In other words, a String is a .NET Object -- no cast is necessary.
You should be able to pass a variable reference to the string, rather than trying to cast it to an Object type, which I don't think is possible in pure VBA.
Dim arg1 as String, arg2 as String
arg1 = "foo"
arg2 = "bar"
AddVariable(arg1, arg2)