The word "convert" may be a bit loose.
The MQL4 language is a C construct, meaning it uses a syntax & structure that's loosly based on C. I would be surprised if you could find a "Converter" for it but it would be reletively simple although time consuming to "Translate" the MQL4 Code to VB.

Example:
MQL4 For loop;
for(i=0;i==15;i++)
{
do something here;
}

Translation to VB;
i=0
For i=1 to 15
Do something here
Next

Hope that helps answer your question.

Manx